Construction of Artificial Wetland for Wastewater Treatment

<div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                  Wastewater that are produced by industries are needed to treat in a proper manner before discharge into public sewer or receiving water bodies because industrial wastewater contain lots of harmful chemicals and pathogens. International and national standards must be followed at the discharge point of industries into receiving water bodies or public sewer. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                       Untreated wastewater or effluent cause severe environmental, social and economic problems when they are directly discharged without pretreatment. The release of wastewater without pretreatment stresses the public sewers. Untreated wastewater contain high pollution load which upset the biological processes. It exceeds the capacity of aerobic repertory microorganisms which involve in the degradation of organic matter in the aeration tank. It has to be given more retention time to reduce the undesirable qualities of the wastewater but it increases the cost of the treatment. It needs storage tank with high capacity which makes more land requirements to handle large wastewater volumes. Therefore pretreatment of industrial wastewater is essential before the discharge into public sewers.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                       Small scale industries and some of large scale industries tend to discharge their wastewater without treatment into receiving water bodies. These wastewater are able contaminate the ground water table which threats health of human. Release of untreated wastewater into surface drinking water sources discharge considerable amount of toxic metals and dyes which affects the ecosystems and human health. Industrial wastewaters that bring sewage as well contain loads of phosphate and nitrate which are capable of accelerating the growth of algae. With time, higher growth of the algae makes the aquatic ecosystem completely die. Some algal species are capable of producing harmful substances that are toxic to animals and human.  This kind of algal growth is known as <b>harmful algal broom</b>. <o:p></o:p></span></div> <span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;">                 Most industries have a combined system for process both industrial wastewater and sewage wastewater which is generated by the sanitation activities of workers in the factories due to the cost effectiveness.</span><br /> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggWWQ1QTCg_KEhAZPdo-4g6bOIwcwmoNqh5evGAJva3pqu43wapJ_OOMm4M0sswuuVoQzSgso1xXfOLZF4dIZic0dm2B-tcVzfa8zrRJ0nMsRaF4S5DqlolRCFB1g7rXNPAUvTo9-5MbnG/s1600/Capture.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggWWQ1QTCg_KEhAZPdo-4g6bOIwcwmoNqh5evGAJva3pqu43wapJ_OOMm4M0sswuuVoQzSgso1xXfOLZF4dIZic0dm2B-tcVzfa8zrRJ0nMsRaF4S5DqlolRCFB1g7rXNPAUvTo9-5MbnG/s640/Capture.PNG" width="635" /></a></div> <span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;"><br /></span> <span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;"><br /></span> <span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;"><br /></span> <br /> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">Wastewater is collected from the all over the industry and passed through a metallic <b>bar screen</b>. It retains the large particles such as straws, glass pieces and sanitary napkins that can damage the pumps and other equipment in the treatment plant. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                           Oil from incoming wastewater is removed in the oil separation tank. <b>API (American Petroleum Institute) separators</b> can be used for better efficient oil separation. Here specific gravity difference between oil and wastewater is the main principle behind the separation. Oil is collected form the surface. Sediment that is settled down at the bottom of the tank is directed to the central sludge management facilities. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                           Then wastewater is transferred to <b>flow equalization tank</b>. As the production cycle of industries varies, water is stored for certain period of time in the flow equalization tank. It produces stable wastewater for downstream process. Temperature of the wastewater is reduced by giving enough retention</span> <span style="font-size: 14.0pt; line-height: 115%;">time in this tank. The variation of the concentration of wastewater throughout the whole tank is avoided by continuous mixing. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                           Coagulant agents such as lime, alum, ferrous Sulfate and ferric Sulfate are added to remove the dissolved solid matter. After addition of coagulant agent, water is rapidy mixed to disperse the coagulant throughout all of the water in the <b>coagulation tank</b>. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                           Then water is transferred into <b>flocculation tank</b>. Here water is gently mixed to allow</span> <span style="font-size: 14.0pt; line-height: 115%;">flocs to form. These flocs are removed by using a <b>sedimentation tank</b>. Chemical flocs are settled down under gravity. They are collected from the bottom of the tank and send for central sludge management facilities.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                           Wastewater is passed into a <b>floatation tank</b> to remove solid particle from the water. It helps to remove very tiny light particles from the water. Here a gas (air bubbles) is introduced and to form scum which is collected from the surface. The sediments that are collected at the bottom are directed to the central sludge management facilities.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                           The biodegradable organic matter in the wastewater is removed by using <b>aeration tank</b>. Here aerobic respiratory microorganisms are employed under aeration. They oxidize organic matter completely into carbon dioxide and water without leaving any residues. External nutrient sources such as canteen waste or cow dung can be added to enhance the efficiency of the microorganisms. Aerobic respiratory microorganisms are also added externally to maintain high <b>F/M (Food to Microorganisms) ratio</b> because when microorganisms are higher than the available food, they tend to form flocs via attaching to each other.  These biological flogs are removed by using another settling tank. Retention time of wastewater is 4-8 hours in the aeration tank. The amount of sediments can be reduced by extending the retention time from 1-2 days.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                           Then wastewater is transferred to secondary clarifier or settling tank. Here biological flocs are settled down under gravity. They are collected from bottom. A portion of sediment is returned back to the aeration tank to as <b>activated sludge </b>to enhance the treatment of incoming wastewater. Remaining portion is disposed as sludge. It can be degraded completely in an anaerobic digester. Unoxidized sludge mostly includes high strength organics such as lignin and cellulose which is unable to degrade by aerobic respiratory bacteria.  Anaerobic digestion of organic matter produces methane which combustible gas which can be used as the alternative fuel for fossil fuel. This sludge also can be send to central sludge treatment facilities to treat with the sludge which is generated by other process.  <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                           After biological treatment of wastewater, it is transferred to another tank for <b>disinfection</b>. Disinfection is used to kill disease cause microorganisms. Chlorine treatment, ozonation and UV treatments are the available method for disinfection. Although use of chlorine is cost effective, excess amount of chlorine produce disinfection by products (DBP) which are carcinogen chemicals. Both UV and ozonation do not leave any chemical residue. But ozonation require highly specialized equipment to produce ozone and contact with water. So UV treatment is relatively cost effective and environmental safe. <o:p></o:p></span></div> <span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;"> </span><br /> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                           These levels of treatment is not enough to release wastewater into public sewers or receiving water bodies because wastewater still contains non degraded organic matter and excess nutrient such as phosphate and nitrate. They can be removed by using different chemical, physical and biological methods. But it has to be combined several method to achieve better tertiary treatment. It is expensive and labor intensive. Therefore <b>construction of artificial wetland </b>solves these problems and gives relatively efficient and environmentally friendly tertiary treatment.</span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhS7tw-3827Q7gC89rU9lHP4AuALAy3iohz_lEHrQw7-gbzVUYvmluT67vf7ojHGDe8HYEzpzRw8W1tg7N4aVJLHExE0akG8r5mD0FJgl3SUwVITGfvKnJWGsY6DIgPGCMv8XkNJN86WXID/s1600/img5.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="382" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhS7tw-3827Q7gC89rU9lHP4AuALAy3iohz_lEHrQw7-gbzVUYvmluT67vf7ojHGDe8HYEzpzRw8W1tg7N4aVJLHExE0akG8r5mD0FJgl3SUwVITGfvKnJWGsY6DIgPGCMv8XkNJN86WXID/s640/img5.jpg" width="640" /></a></div> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">Wetland system consists mainly there components such as surface substrate,</span> <span style="font-size: 14.0pt; line-height: 115%;">macrophytes and microbial communities. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                          A gavel layer is applied as the top layer of surface substrate. Beneath the gavel layer a coarse media is applied.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                          Rooted emergent macrophytes such as cattle tails are planted in the coarse media. They produce aerial stem with underground extensive fibrous root system.  These the macrophytes support the growth of microbial communities via association with their root systems and remove certain pollutants from the water. The plants uptake the excess nutrient which is able accelerates their growth from the wastewater. Some plants are capable of absorbing toxic metal of the water such as <b><i>Ipomoea aquatic</i></b>.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                        The microorganisms help to further removal of organics. They plays important role for the removal of excess nutrients. Ammonium ions are removed from the wastewater by denitrification. Oxygen leaks from the rhizomes into the nearby waster where the aerated zone is located. In aerated zones, ammonium ions are oxidized into nitrite by <b><i>Nitrosomonas</i></b> then nitrite is further oxidized intro nitrate by <b><i>Nitrobactor.  </i></b>Then these nitrates are reduced into nitrogen gas which expels from water into the atmosphere by <b><i>Thiobacillus dentrificans </i></b>in the anaerobic zone.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><span style="font-size: 14pt;">                           </span><span style="font-size: 14pt;">In addition above biological process, wetland use physical and chemical methods to remove the pollutants from the wastewater. Main physical processes are sedimentation and filtration. Above gavel and coarse media of the wetland traps the remaining sediment in the incoming wastewater through straining. Volatile organic compounds (VOC) such as phenolic compounds which are resistant to remove during primary and secondary treatment are subjected to volatilization. Those VOCs diffuses from the wastewater from atmosphere due to the action of the photo energy. Chemical process includes the sorption, redox reactions, chemical precipitation and hydrolysis.</span> <o:p></o:p></span></div>

Construction of Artificial Wetland for Wastewater Treatment

                  Wastewater that are produced by industries are needed to treat in a proper manner before discharge into public sewer or r...

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Microbiological Analysis of Potable Drinking Water

<div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwh-9Dv2ExYRITS5L41ZCtvovZ-cA4BGpDkF8MjosSFj3EG4jIMWOkN3h7oHloQgkJ6UwCXI2jMEevpG7p_HYAxHr-m9fDBXG9QhP19dcAmTyAMwvD3uYAA-pv4t52gtOYI11p7z-5y0y6/s1600/img1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="384" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwh-9Dv2ExYRITS5L41ZCtvovZ-cA4BGpDkF8MjosSFj3EG4jIMWOkN3h7oHloQgkJ6UwCXI2jMEevpG7p_HYAxHr-m9fDBXG9QhP19dcAmTyAMwvD3uYAA-pv4t52gtOYI11p7z-5y0y6/s640/img1.jpg" width="640" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">Drinking water sources can be accidently contaminated by human fecal pollution. But release of small quantity of fecal matter does not cause serious health problems because it is highly diluted within the natural water bodies. If water bodies are once fecal polluted, it contains pathogens of fecal origins.  This pathogen may include protozoan cysts, nematodes larvae, nematode eggs, viruses, bacteria and fungi. But it is difficult to test for each and every above organism so test for indicator organisms such as tests for <i>E coli</i> is done. It is an intestinal microorganism that lives in human and most animal bodies. <i>E coli</i> releases through the fecal matter into aquatic water bodies. They do not die as soon as they release from the human body. But they cannot survive for many days in the water due to low nutrient availability. It is assumed that fecal origin pathogens also have similar duration of survival within aquatic water bodies.</span> <span style="font-size: 14.0pt; line-height: 115%;">According to WHO, drinking water cannot contain at least one E coli. If drinking water contain at least one E coli, it is not suitable for human consumption.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                      Testing for E <i>coli</i> is cost effective and time saving. If <i>E coli</i> are present, it indicated that there is high probability of presence of fecal origin pathogens. But even if direct testing for <i>E coli</i> is cost because electricity has to be applied to inoculate the microorganisms in the water sample at high temperatures  in order to test for <i>E coli</i>. So initially testing for coliform is done. Coliform is a group of bacteria that are capable of fermentation lactose and producing acids and gas. Coliforms are gram negative and rod shaped bacteria. <i>E coli</i> are also one of the members of coliform. If the result of coliform test is negative, there is no need of further testing. Therefore water can be released for human consumption. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                Testing for <i>E coli</i> is done in three steps such as presumptive test, coliform test and conform test. In presumptive test, MaConkey broth is used the culture media. MaConkey broth media acts as the selective and differentiate medium for isolation of gram negative lactose fermentative bacteria.  It is comprised of lactose as the carbon source, peptone as the nitrogen and other nutrient source, bile salt, pH indicator and NaCl. Bile broth is added to suppress the growth of gram positive bacteria. Bromo cresol purple or neutral red is added as the pH indicator to observe to acid production of bacteria. If Bromo cresol purple is added, it changes its color as yellow due to the acid production. If neutral red is added as the pH indicator, it changes it color as dark red due to the acid production. NaCl is added to t maintain the osmotic balance of the medium. <o:p></o:p></span></div> <br /> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                  Here five test tubes are prepared with 9 mL of double strength MaConkey broth and 1ml of water sample to prepare 10</span><span style="font-size: 24.0pt; line-height: 115%;">◦ </span><span style="font-size: 14.0pt; line-height: 115%;">series.</span><span style="font-size: 24.0pt; line-height: 115%;"> </span><span style="font-size: 14.0pt; line-height: 115%;">Then another five test tubes are prepared with 9mL of single strength MaConkey broth and 1ml of water sample to prepare 10^-1 series. 1mL of water sample is taken into another test tube containing 9mL of peptone to dilute water to 10^-1. Then from that test tube 1mL is added to five test tubes filled with 9mL of single strength MaConkey broth to prepare 10^-2 series. These test tube series are inoculated at 37◦C for 24-48 hours. Color change due to the acid production and gas collected in the Durham tube are taken as the positive result of this test.</span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLbeM1ayOJ50HsMffdn9DOSCd9qQtGOgcQB0-UJ3RuobVQd80AiO6JryKc6qxNoAglzRNWM_Xwou86m3gHakGFIhevXtk_U8FXY84BKlxr9tHOuu-5U3-CbH_9qaDZdDsp5Ag5IVwxB1Dt/s1600/img2.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="275" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLbeM1ayOJ50HsMffdn9DOSCd9qQtGOgcQB0-UJ3RuobVQd80AiO6JryKc6qxNoAglzRNWM_Xwou86m3gHakGFIhevXtk_U8FXY84BKlxr9tHOuu-5U3-CbH_9qaDZdDsp5Ag5IVwxB1Dt/s400/img2.PNG" width="400" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">If the result of presumptive test is negative, there is no need of further testing.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"> It indicated that there is no coliform that means there are no E coli. If results are positive, it indicates the presence of coliform. So further testing is needed to confirm whether presence or absence of coli.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><span style="font-size: 14pt;">                       </span><span style="font-size: 14pt;">The test tubes those shows positive results are used to inoculate in the conform test. Two methods are available such as BGLB broth or EMBA. BGLB broth means brilliant green lactose bile broth. Here lactose also is added as carbon source for bacterial fermentation. Brilliant green dye suppress the growth some selective gram negative bacteria. Bile suppresses the growth of gram positive bacteria. One set of BGLB broth containing test tube are inoculated at 37◦ C for total coliform. Total coliform contain both environmental coliform and fecal coliform. Another set of BGLB broth containing test tube are inoculated at 44◦ C for fecal coliform. Gas production in the Durham tube is taken as the positive results in this test.</span></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixIQE4k4bkvZ9R_zPGm88b7ziYu3qEfnsarMlYuYqooHd-kXsHgXS0BtoXgcfPCg4AZq6H2yOgmjL7yfnv6XAxVj_W8r3vhlE6DsVVktNRqLb1NooOR3eAat67FoSBAjF8Y-kBQGjfKHD0/s1600/img3.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixIQE4k4bkvZ9R_zPGm88b7ziYu3qEfnsarMlYuYqooHd-kXsHgXS0BtoXgcfPCg4AZq6H2yOgmjL7yfnv6XAxVj_W8r3vhlE6DsVVktNRqLb1NooOR3eAat67FoSBAjF8Y-kBQGjfKHD0/s400/img3.PNG" width="400" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><span style="font-family: Calibri, sans-serif; font-size: 14pt; line-height: 115%;">Plate containing EMBA agar is used to conform the presence of <i>E coli</i>. Inoculum from the test tubes that shows positive results are taken into plates for inoculate at 37◦C for 24-48 hours. EMBA means Eosin Methylene Blue Agar.</span><span style="font-family: Calibri, sans-serif; font-size: 11pt; line-height: 115%;"> </span><span style="font-family: Calibri, sans-serif; font-size: 14pt; line-height: 115%;">Eosin Methylene Blue dyes suppresses the growth of gram positive bacteria. Agar is added as the solidifying agent. Lactose is added as the carbon source for bacterial fermentation. It gives characteristic green color with metallic sheen if strong acid producers are present such as <i>E coli</i>. It gives pink colored colonies if weak acid producers are present such as <i>Enterobacto</i>r. Non lactose fermentative does not give any color.</span></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiGJp6mWZ3xiZ6w9tgtLEo8dWaXtD3SjuMTrLuO-mP_felBVQP_5ld7YmsbyKxsXSTTIaI5e8mvwi7vbc_dn7Sn4sVVIAg3XKbnGBPcFSKh7jQnsOs3JTFhNIWh9Vqny2WGOYU4aEonBXHf/s1600/img4.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="228" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiGJp6mWZ3xiZ6w9tgtLEo8dWaXtD3SjuMTrLuO-mP_felBVQP_5ld7YmsbyKxsXSTTIaI5e8mvwi7vbc_dn7Sn4sVVIAg3XKbnGBPcFSKh7jQnsOs3JTFhNIWh9Vqny2WGOYU4aEonBXHf/s400/img4.PNG" width="400" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"> If results from conform test is negative, there is no fecal coliform. So water can be released for human consumption. But if results are positive, further testing is needed because In addition to <i>E coli, Enterobacto</i>r also shows positive results for confirm test.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><span style="font-size: 14pt;">                          </span><span style="font-size: 14pt;">Then complete test is done to confirm exactly presence of </span><i style="font-size: 14pt;">E coli</i><span style="font-size: 14pt;">. IMViC tests are done. IMViC means Indol Methylene red VP Citrate tests. </span><i style="font-size: 14pt;">E coli</i><span style="font-size: 14pt;"> give positive results for Indol and Methylene test. In Indol test, only E coli is able to digeste tryptone because only </span><i style="font-size: 14pt;">E coli </i><span style="font-size: 14pt;">tryptonase enzyme to form Indol ring. As Indol ring cannot be observed due to the colorless, knovas reagent is added. If Indol ring is present, it appears in red in color. </span><i style="font-size: 14pt;">Enterobactor</i><span style="font-size: 14pt;"> gives positive results for VP and Citrate tests. If the results of complete test are also positive, it indicated that presence of </span><i style="font-size: 14pt;">E coli</i><span style="font-size: 14pt;">. So water cannot be released for human consumption due to the possibility of presence of fecal origin pathogens.</span> <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1zOk5Y3EkIstm16EQdDF6G8NqyfhT0NCKfD_h97y-kN6xEIIw4wyB0x-jmZ5DC8YYd8HXZ5uSGsHZmMrUPIylIc2HEELb-8kUoPKmzByLeGuhGZ8tWe_2JfTh_ko_P1Z4XxdI3rhdxeAr/s1600/img.PNG.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="232" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1zOk5Y3EkIstm16EQdDF6G8NqyfhT0NCKfD_h97y-kN6xEIIw4wyB0x-jmZ5DC8YYd8HXZ5uSGsHZmMrUPIylIc2HEELb-8kUoPKmzByLeGuhGZ8tWe_2JfTh_ko_P1Z4XxdI3rhdxeAr/s400/img.PNG.jpg" width="400" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div>

Microbiological Analysis of Potable Drinking Water

Drinking water sources can be accidently contaminated by human fecal pollution. But release of small quantity of fecal matter does not ...

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Enumeration Techniques of Bacteria in Microbiology

<div class="MsoNormal"> <br /></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                    Enumeration is the estimation of the number bacteria in a sample such as water sample or food sample</span><span style="font-size: 20.0pt; line-height: 115%;">. </span><span style="font-size: 14.0pt; line-height: 115%;">Enumeration techniques help to determine the growth rate and death rate of bacteria</span><span style="font-size: 20.0pt; line-height: 115%;">. </span><span style="font-size: 14.0pt; line-height: 115%;">It gives the information about the degree of contamination of pathogenic microorganisms in MPN test. </span><span style="font-size: 20.0pt; line-height: 115%;"> <b><o:p></o:p></b></span></div> <div class="MsoNormal"> <span style="font-size: 20.0pt; line-height: 115%;">                </span><span style="font-size: 14.0pt; line-height: 115%;">Direct methods and indirect methods used for enumeration. Direct enumeration methods include pour plat, spread plate, cell chamber and florescent dyes.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                        Pour plate method uses 1mL of inoculum from the samples. 15mL of molten agar at 45◦ C and inoculum are added to plate and mixed by rotating it on the bench top. It is inoculated for 24-48 hours at 35◦ C. Bacterial colonies can be found both on surface and inside of the agar medium. These bacterial colonies are used to estimate number of bacteria in the initial sample. Pour plate methods help to isolate the microorganisms in the sample to isolate based on the oxygen availability. Aerobic respiratory bacteria can be found on the surface of agar. Microaerophilic bacteria can be found the inside of the agar. Anaerobic bacteria can be found at bottom of the agar. Bit pour plate method have some disadvantages too. The aerobic respiratory bacteria those are trapped inside the agar cannot survive. Heat sensitive bacteria may kill due to the high temperature of melting agar.<o:p></o:p></span><br /> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhEa4W_VMLNCgQ5k4BVwoc8i1otvHb45IUc727kc1HKUPIyXGTbwPXJj7UicLereJIjkARIRr5Hbm6Mw1cn5yMYASq61b6AYxUAsjULgGl3JPWg4UFPcioi70ssTMRvo_LVMq33f2_LxwYb/s1600/Diagram-4.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="308" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhEa4W_VMLNCgQ5k4BVwoc8i1otvHb45IUc727kc1HKUPIyXGTbwPXJj7UicLereJIjkARIRr5Hbm6Mw1cn5yMYASq61b6AYxUAsjULgGl3JPWg4UFPcioi70ssTMRvo_LVMq33f2_LxwYb/s640/Diagram-4.jpg" style="cursor: move;" width="640" /></a></div> <span style="font-size: 14.0pt; line-height: 115%;">                       </span><br /> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span> <span style="font-size: 14.0pt; line-height: 115%;">                       Spread plate method use relatively lower size of inoculum such as 0.1ml from sample compare to the pour plate method. ImL of inoculum form the water sample is transferred to an agar plate. Then sterilized glass spreader is used to spread the inoculum over the surface of agar. It is also inoculated for 24-48 hours at 35◦ C. Bacterial colonies only grow on the surface of agar in spread plate method. If it is inoculated under aerobic conditions, aerobic respiratory bacteria can be isolated and estimated. If it is inoculated under anaerobic conditions, anaerobic respiratory bacteria can be isolated and estimated.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              But both pour plate method and spread plate method do not give accurate results because these artificial cultural media are unable to provide extreme environmental conditions and nutrients. So these enumeration techniques do not estimate the accurate number in the samples. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              In above both pour plate method and spread plate method, colony forming units (CFU) are taken into considered to estimate the number bacteria present in the initial sample. Colony forming units are the single microorganisms that are able to from visible single colony. So it is assumed that all colonies in the plates are made by single bacterium cell. Only plates with colony in-between 30-300 are counted.<o:p></o:p></span></div> <span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;">            A dilution series is prepared in both methods as follows. Inoculum from the initial sample is transferred into test tube with 9mL of broth by using sterilized pipette. Its concentration is 10^-1. Then 1mL of first dilution is added to another into test tube with 9mL of broth by using another sterilized pipette.</span><span style="font-family: "calibri" , "sans-serif"; font-size: 11.0pt; line-height: 115%;"> </span><span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;">Its concentration is 10^-2</span><span style="font-family: "calibri" , "sans-serif"; font-size: 11.0pt; line-height: 115%;"> </span><span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;">. Then 1mL of second dilution is added to another into test tube with 9mL of broth by using another new sterilized pipette. Its concentration is 10^-3</span><span style="font-family: "calibri" , "sans-serif"; font-size: 11.0pt; line-height: 115%;"> </span><span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;">. Then 1mL of third dilution is transferred to another into test tube with 9mL of broth by using another sterilized pipette. Its concentration is 10^-4.. Then 1mL of forth dilution is added to another into test tube with 9mL of broth by using another sterilized pipette. Its concentration <span style="font-family: "calibri" , sans-serif; font-size: 18.6667px;">is 10^-5.</span></span><br /> <span style="font-family: "calibri" , sans-serif;"><span style="font-size: 18.6667px;"><br /></span></span><span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;"></span> <br /> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi_5R_fEJIW60R-uJKPv4i7xAiqc-kbXgvG46ovcSrPDhT3zjt_vNkJMOXFrn1ECmsS7xwWd8uyootqSw_ybW7jvgw7JFGoQyAAOTT8YktdndPmHYKnE2YkIFuou1uDIt4Xwdg4c5HDKGaj/s1600/NYMU14_safety_2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="350" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi_5R_fEJIW60R-uJKPv4i7xAiqc-kbXgvG46ovcSrPDhT3zjt_vNkJMOXFrn1ECmsS7xwWd8uyootqSw_ybW7jvgw7JFGoQyAAOTT8YktdndPmHYKnE2YkIFuou1uDIt4Xwdg4c5HDKGaj/s640/NYMU14_safety_2.jpg" width="640" /></a></div> <div class="separator" style="clear: both; text-align: center;"> <br /></div> <div class="separator" style="clear: both; text-align: center;"> <br /></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">Streak plate method cannot be used for enumeration because the volume of loomful is known.                                        <o:p></o:p></span></div> <br /> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                  </span><span style="font-size: 14pt;"> </span><span style="font-size: 14pt;">Cell chamber method uses a petrioff to estimate number of bacteria. It is able to count the bacteria directly within the squares of petrioff slide and estimate according to the initial volume.</span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                   Fluroscent dye method is used to estimate the total microorganisms in samples such as soil and water. It gives accurate estimation of both living and dead bacteria. Acridine dye is applied to observe and estimate the bacteria.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                     MPN test and turbidity are the indirect methods of enumeration. In turbidly technique, turbidity of sample is measured and transferred this measurement into cell number. A plate series is prepared and measured the turbidity of them.  Standard curve is plotted and takes the number of bacterial cell in the initial sample aid in the graph.  <o:p></o:p></span></div> <div class="separator" style="clear: both; text-align: center;"> </div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                     A series of dilution is prepared for MPN test. It is used in the estimate of number <i>E coli</i> present in fecal contaminated water sample. Inoculum of initial water sample is transferred as 1mL, 0.1mL and 0.01mL into spate test tube containing broth culture. Five replications for each dilution are made to increase accuracy. Every tube that shows growth is taken as the positive results. It may be acid production and gas collection in Durham tube. Ratio between positive results of each dilution is taken as MPN ratio.  Then number of bacteria in the initial water sample is taken from a MPN table which is made according to various other testing and based on statistics by using MPN ratio.<o:p></o:p></span></div> <span style="font-family: "calibri" , "sans-serif"; font-size: 14.0pt; line-height: 115%;"></span><br /> <div class="separator" style="clear: both; text-align: center;"> <br /></div> <div class="separator" style="clear: both; text-align: center;"> <br /></div> <div class="separator" style="clear: both; text-align: center;"> <br /></div> <div class="separator" style="clear: both; text-align: center;"> <br /></div> <br />

Enumeration Techniques of Bacteria in Microbiology

                    Enumeration is the estimation of the number bacteria in a sample such as water sample or food sample . Enumeration te...

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Nitrogen Cycle in Microbiology

<div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjrCyOE8tKtV7aP1FiuDkcTkIeY-1Ypli_XBpNePXuLx6xnxKu6TUGgjqtsYs9QfCDT397qWW5r37971ODNay5Ax-KjtbEE6_pCJSNeklN7Ha_8Gc1Q_qdzsrOr5_q1YLim2NbQfXAdclFM/s1600/Nitrogen+Cycle+in+Microbiology.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="636" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjrCyOE8tKtV7aP1FiuDkcTkIeY-1Ypli_XBpNePXuLx6xnxKu6TUGgjqtsYs9QfCDT397qWW5r37971ODNay5Ax-KjtbEE6_pCJSNeklN7Ha_8Gc1Q_qdzsrOr5_q1YLim2NbQfXAdclFM/s640/Nitrogen+Cycle+in+Microbiology.jpg" width="640" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">Nitrogen is the most available gas in the atmosphere. It accounts roughly for 70% atmosphere. Nitrogen is found as nitrogen gas which is inert form. So it needs large amount of energy to break the bond between the two nitrogen atoms. This atmospheric nitrogen fix into nitrate via two methods such as atmospheric fixation and biological fixation.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                       In <b>atmospheric fixation of nitrogen</b>, lighting releases a considerable amount of energy that is enough for the breakdown of the bond of nitrogen gas. Then nitrogen atoms react with water in the rain and convert into nitrate ions. These nitrate ions reach to the soil through the rain.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                       Certain bacteria those inhibit in the soil involve in the <b>biological fixation of nitrogen </b>into ammonium ions. Some nitrogen fixing bacteria are free living. Ex: <i>Azotobactor</i>, <i>Bacillus polymyxa</i>. Other nitrogen fixing bacteria form symbiotic relationship with legume plants. Ex: <i>Rhizobium</i> sp. They fix atmospheric nitrogen into nodes on the roots of legume plant. Those nitrogen are available to the plant when roots are dead or they add nitrogen directly when legume plant are buried or grown as an intercrop. Cyanobacteria are another group that is capable of fixing atmospheric nitrogen. They also form symbiotic relationship with roots of certain plant such as <i>Cycad</i>,<i> Azolla</i> and liverworts. Among them, <i>Anabena-Azolla</i> relationship is more efficient than legume plants in nitrogen fixation so farmers use <i>Anabena-Azolla</i> in their rice paddies in order to increase their yield.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                       <b>Decomposition of nitrogenous organic matter</b> releases ammonium ion to the soil. Organic matter contains protein those are rich in ammonium compounds.  Leaf litter, root decomposition and animal excretions make the soil fertile via release of ammonium. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Then ammonium ions in the soil are used as the substrate by ammonium oxidizing bacteria such as <b><i>Nitrosomonas</i></b><i> </i>in the presence of oxygen. They oxidize this ammonium into nitrite ions. They do this oxidation to take electron to run the electron transport chain to ATP syntheses. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Those nitrite ions are used as substrate by nitrite oxidizing bacteria such as <b><i>Nitrobactor </i>i</b>n the presence of oxygen. They oxidize nitrite into nitrate which the preferable form of plant to be absorbed. They do this oxidation to take electron to</span> <span style="font-size: 14.0pt; line-height: 115%;">run the electron transport chain to synthesis ATP. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                             The oxidation or conversion of ammonium ions into nitrate ions refer to as the <b>nitrification</b>. Nitrification helps to increase the soil fertility. Aeration is the only accelerating factor that is responsible for the nitrification. Tilling helps to aeration of the soil. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              In the absence of oxygen, certain facultative anaerobic microorganisms in the soil such <b><i>Thiobacillus dentrificans</i></b> use these nitrate ions as terminal electron acceptor in their anaerobic respiration. They reduce nitrite into nitrogen gas which expel from the soil into atmosphere. The process that convert nitrate into nitrogen gas is called as <b>denitrification</b>. Denitrification makes the soil infertile. But as <i>Thiobacillus dentrificans</i> is facultative anaerobe, they shift into aerobic respiration when soil is aerated. Therefore aeration of soil helps to stop the denitrification of soil. <o:p></o:p></span></div> <br /> <div class="MsoNormal"> <br /></div>

Nitrogen Cycle in Microbiology

Nitrogen is the most available gas in the atmosphere. It accounts roughly for 70% atmosphere. Nitrogen is found as nitrogen gas which i...

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Bio Leaching of Metal Ions Form Low Grade Metal Depositions

<div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAxTvyDNjyJiaqSHXOqUZ5zZbNBP2MGks04MkZR-_zImEPP5gvJ8h6QwFzWUuWPgX-Vykij-SV2co7Ey-FEvTHmKZha5BbiHs7kR1cfw4PLnO9ix2dvwwdMBY_S6N5nPkRuhjV9j0X0jCF/s1600/img6.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAxTvyDNjyJiaqSHXOqUZ5zZbNBP2MGks04MkZR-_zImEPP5gvJ8h6QwFzWUuWPgX-Vykij-SV2co7Ey-FEvTHmKZha5BbiHs7kR1cfw4PLnO9ix2dvwwdMBY_S6N5nPkRuhjV9j0X0jCF/s640/img6.jpg" width="640" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                         </span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">  There are metal depositions in the world with low concentrations so they refer to as <b>low grade metal depositions</b>. Therefore it is non-effective to extract metal ions by using chemical extractions. Therefore metal ions from low grade depositions are extracted by using metabolic activates of bacteria.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;">Copper extraction</span></b><span style="font-size: 14.0pt; line-height: 115%;">: Low grade Copper depositions are known as low grade copper ore. Copper is available as Covelite (CuS). Covelite that is extracted from the underground deposition are pilled as heap. Concentrated sulfuric acid is added to the top the heap.  Usually Covelite are associated with pyrite (Fe2S).  Pyrite plays a major role of copper extraction process. Sulfur oxidizing bacteria such as <i>Thiobacillus thioxidans</i> use sulfide of the pyrite (Fe2S) as their substrate for their ATP synthesis. They oxidize sulfide into sulfate. This reaction releases ferrous ion from the mineral. Then these ferrous ion is used the substrate by <i>Acidothiobacillus thioxidans</i>. They oxidize ferrous ion into ferric ion. These ferric ions are collected and added to the top of heap. These ferric ions undergo a redox reaction with Covelite. Ferric is reduced back into ferrous. Sulfide of Covelite is oxidized into sulfate. These reaction releases cupric ion. A scarab metal is put to the tank to reduce the cupric ion into copper metal. Copper metal can be collected from the bottom of the tank. Ferrous ions are again oxidized into ferric by iron oxidizing bacteria.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <br /> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;">Uranium extraction</span></b><span style="font-size: 14.0pt; line-height: 115%;">: In the environment, uranium depositions are found in the form of Uraninite (UO2) which water insoluble. Uraninite depositions are piled into heap.</span> <span style="font-size: 14.0pt; line-height: 115%;">Pyrite also plays important role in Uranium extraction. Sulfur oxidizing bacteria such as <i>Thiobacillus thioxidans</i> use sulfide of the pyrite (Fe2S) as their substrate for their ATP synthesis. They oxidize sulfide into sulfate to take electron to run electron transport chain. This reaction releases ferrous ion from the</span> <span style="font-size: 14.0pt; line-height: 115%;">pyrite (Fe2S). </span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">Then these ferrous ion is used the substrate by iron oxidizing bacteria such as <i>Acidothiobacillus thioxida</i>ns. They oxidize ferrous ion into ferric ion. These ferric ions are collected and added to the top of the heap. These ferric ions undergo a redox reaction with Uraninite. Ferric is reduced into ferrous. Uraninite (IV) is oxidized into Pitchblende (VI) which less water soluble. Pitchblende can be collected from the bottom of the tank. Ferrous ions are again oxidized into ferric by iron oxidizing bacteria.<o:p></o:p></span></div>

Bio Leaching of Metal Ions Form Low Grade Metal Depositions

                            There are metal depositions in the world with low concentrations so they refer to as low grade metal depo...

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Preparation of culture media

<div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlcUm8ssaxPBP_ei0PDpy7WDrF1viDrWIYcEpqHYcT8VkxaQSY42yHJNiOdbyGFsKMGSKay9xoTiUmZLT2Ba5uV0Sjm0VyTbk4CuQJKhc6-_WiFqpAbkUzDzvF2TAKsGRsm5JpALqS707t/s1600/culture+media.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="380" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlcUm8ssaxPBP_ei0PDpy7WDrF1viDrWIYcEpqHYcT8VkxaQSY42yHJNiOdbyGFsKMGSKay9xoTiUmZLT2Ba5uV0Sjm0VyTbk4CuQJKhc6-_WiFqpAbkUzDzvF2TAKsGRsm5JpALqS707t/s640/culture+media.jpg" width="640" /></a></div> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;">                 </span></b></div> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;"><br /></span></b></div> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;">Culture media</span></b><span style="font-size: 14.0pt; line-height: 115%;"> are the artificial media that are designed to grown microorganisms in the form of liquid, semi-liquid or solid media.                                                          <b>Importance</b>: Culture media helps to isolate one particular microorganism group from a mixture. It provides reliable ways to estimate number of microorganisms. It helps to manipulate microorganisms to some genetic studies. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                            Microorganisms in the environments depend on various factors such as nutrients, oxygen, temperature and moisture for their survival, growth and reproduce.  When</span> <span style="font-size: 14.0pt; line-height: 115%;">Chemoheterophic microorganisms are grown in artificial medium in the laboratory, it has to be supplied externally carbon source, nitrogen source and energy source. Chemoheterophic microorganisms refer to as oxidize organic or inorganic substrate to produce ATP and start their carbon nutrition form organic compounds which are produced from carbon dioxide by autotrophs.  <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                             Culture media must provide basic requirements for microorganisms those are needed to grow.  Agar is added as the solidifying agent. 1.0-1.5% agar is added to prepare solid culture media. Semi-sold culture media are prepared by adding 0.5%agar. <b>Carbon source</b> is added as the oxidizable substrate for microorganisms to synthesize their ATP. Lactose is usually added as carbon source. <b>Nitrogen and other nutrients</b> are provided as beef extract. Usually peptone is added to provide both carbon and nitrogen with other nutrients to the medium. Peptone is a mixture of partially digested protein of meet intrusion. It contains proteins that are readily digestible for microorganisms.  <b>It fastidious microorganisms</b> which has complex nutrients requirement, it has to be supplied special nutrients. Serum or yeast extract or beef extract is added to fulfill their special nutrient requirements.  <b>It selective culture media</b> is needed to prepare to isolate one microorganism group, antibiotics is added to kill other microorganisms. In addition to those sources, electron donors and acceptors and growth promoting vitamins have to be added.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                  <b>Consistency of the medium</b> is modified by adding solidifying agent such as <b>agar, gelatin or albumin</b>. Earlier gelatin was used as solidifying agent. But gelatin had some disadvantages. It is liquid at 37◦ C. It is digested by many bacteria. Therefore later agar which is extracted from red algae is used as solidifying agent. Solid agar melts at 85◦ C. it is not preferably digested by bacteria. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                  In addition above nutrients requirements, chemical and physical conditions also must be adjusted for growth of microorganisms.   Majority of microorganisms are able to survive at neutral pH. Few prefer extremely acidic or basic pH. Oxygen is also major limiting factor that affect the growth of microorganisms. Aerobic, facultative and microaerophilc are able to survive and grow in the presence of oxygen. But anaerobic</span> <span style="font-size: 14.0pt; line-height: 115%;">microorganisms cannot survive in the presence of oxygen. Therefore if anaerobic microorganisms are needed to grow, culture media must be free of oxygen.  Addition of reducing substance, displacement oxygen by carbon dioxide and boiling are the methods that help to create oxygen free environment. Microorganisms show maximum growth at their optimum temperature. According to the temperature requirements, microorganisms are categorized into three groups such as psychrophilic, mesospheric and thermophile. Psychrophilic grow and reproduce at 0◦ C. Mesospheric grow and reproduce at 15-30◦ C. Thermophilc grown even greater than above 90◦ C. Moisture content also effects the growth of microorganisms. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                               <b>Nutrient agar (NA)</b> is the general purpose media for bacteria in the laboratory. It is prepared by adding beef extract (3g), peptone (5g), agar (15g) and distils water (1000ml). The pH of the culture media is 6.8±0.2. Bacteria in the free environment are inoculated at 25◦ C for 48 hours. But human pathogens are inoculated at 37◦ C because of inner body temperature of human.  Some bacteria show growth even after 24 hours because growth rate depends on the species. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                <b>Dextrose potato agar (DPA)</b> is the general purpose media for fungi in the laboratory. It is prepared by adding dextrose (20g), potato extract (4g) and agar (15g). Fungi are inoculated at 25◦ C for 5days. Fungi have relatively lower growth rate compare to the bacteria. The pH of the culture media is 6.2.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                Culture media are classified according to their consistency, usage, purpose and nutrient composition. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                According to <b>consistency</b>, culture media are divided into three categories such as <b>liquid, semi- solid</b> and <b>solid</b>. Broth culture is the example for liquid media. It helps to observe motility and characteristics of bacteria. Semi- solid media are prepared by adding 0.5%agar. It gives the advantage of observing motility of bacteria. It provides ideal environment for inoculating microaerophilic bacteria. Solid media are prepared by adding 1.0-1.5% agar. Slop media (slunt) and deep stab are the example for solid media. In slunt, slope provides the high surface area for inoculation. Slunt is used to inoculate aerobic bacteria while butt is used to inoculate anaerobic bacteria. Deep stab is used to observe the growth of bacteria according to oxygen availability. Top area of deep stab is used to inoculate aerobic bacteria while bottom of the deep stab is used to inoculate anaerobic bacteria. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                Culture media are categorized into two groups such as <b>general purpose and special purpose media</b> based on the <b>purpose</b>. General purpose media is comprised with basic nutrients requirements. These media contains only carbon source and nitrogen source .Special purpose media supports the growth of fastidious microorganisms. So in addition to carbon source and nitrogen source, those media contain special nutrients.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                Culture media are categorized into <b>simple, complex and defined (or synthesis)</b> according to the <b>nutrient composition</b>.  Simple media supports the non-fastidious microorganisms. It includes peptone, water and nutrient agar. Complex media supports the fastidious microorganisms. Exact chemical composition of complex media is unable to find. Blood agar is one of the examples for complex media. Defined (or synthesis) media is used for researches. Exact chemical composition of the defined media is known. <o:p></o:p></span></div> <br /> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                Culture media are classified into basal, enrich, selective or isolation, differentiate, reducing and transport based on their usage<b>. Basal media</b> support the growth of non-fastidious microorganisms. It is also made of peptone, nutrient broth or nutrient agar. <b>Enriched media</b> are used to grow fastidious microorganisms. Their special nutrient requirement is fulfilled by addition of blood serum, egg york into basal media. <b>Differential/Indicator</b> media helps to isolate one microorganisms form other microorganisms. Their metabolic activates help to isolation of them. As an example, neutral red or bromo cresol purple is added as the indicator to detect the acid production in coliform test. Coliform are the special group of bacteria that are able to produce acids during their sugar fermentation process<b>. Selective and enrichment media</b> are used to inhibit the growth of untargeted or unwanted microorganisms in a mixture. Addition of antibiotics and alteration of pH of the media help to inhibit of the untargeted or unwanted microorganisms. As an example, Brilliant Green Lactose Bile (BALB) broth contain bile to suppress the growth of gram positive bacteria in the confirm test of fecal coliform. <b>Transport media</b> are useful for bringing clinical sample into the laboratory. Those media supports to inhibit the overgrowth of unwanted microorganisms in a pathogen mixture.  Saline is added to prevent the desiccation. Charcoal is added to neutralize the inhibitory factors. <b>Reducing or anaerobic</b> media are used for inoculation of anaerobic microorganisms. Oxygen can be removed by using either physical or chemical methods. As a psychical method, boiling removes oxygen from the media. Red hot iron filling can be added to remove oxygen as a chemical method.<o:p></o:p></span></div>

Preparation of culture media

                  Culture media are the artificial media that are designed to grown microorganisms in the form of liquid, semi-liqui...

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Endospore staining

<div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;">Endospore</span></b><span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;"> is domanet strucure which have no or less metabolic activities. Bactiers form endospre when environemntal conditions are  unfavorable to them such as  high oxygen concentraion, temperature, heat and desssication. Endospore cannot be killed by just boilling at 100◦C but at 121◦C. <b><i>Bacillus, Clostridium </i></b>and<b><i> Sporalactobacillus</i></b><i> </i>are examples for endospore froming bacteria<i>. <o:p></o:p></i></span></div> <br /> <div class="MsoNormal"> <i><span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;">                             </span></i><span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;">The outermost layer of the endopsore is proteinaceous <b>coat</b>. Bneeth coat, there is a a very thick layer of peptidoglycan which is called as the <b>cortex</b>. Under cortex, <b>grem cell wall</b> reside. After endospire germination, grem cell wall become the cell wall fo bacterium. Bneath gren cell wall, <b>inner membrane</b> is founsd. It act as adverse premeability barrier. The <b>core </b>exsits in the center of the endopore. The core is the dehydreted DNA of the bacterium cell.</span></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFLxvMuX-FFJm5SOrIV2Uk3hCXE7Grf_wTZWPQNWCBeRi6cVcUd2VoICOgHTDtx0W-eyX4EffQFFFHxfeYqw53ivE0IdoPiefnc04y0Oq4OInaWoMMvibazaRVkkxDkphIgCUQoSVgb2z0/s1600/img3.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="552" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFLxvMuX-FFJm5SOrIV2Uk3hCXE7Grf_wTZWPQNWCBeRi6cVcUd2VoICOgHTDtx0W-eyX4EffQFFFHxfeYqw53ivE0IdoPiefnc04y0Oq4OInaWoMMvibazaRVkkxDkphIgCUQoSVgb2z0/s640/img3.jpg" width="640" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;"><br /></span></div> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;">Endospore  staining</span></b><span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;"> is a differentiate staining technique which is used to differentiate bacteria into two groups such as endospore forming baetria and non endospore forming bateria. Endospore is stained in green while vegetative cell is stained in pink. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;"><b><span style="font-size: 14.0pt; line-height: 115%;">Position of endospore</span></b><span style="font-size: 14pt; line-height: 115%;">: The position of endospore inside the vegetative cell varies from one bacterium species to another as follows.</span> <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;"><br /></span></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLbahiysrBBDBs_wEQfCyQPxcvYukSN_3UKCDfN3Geg1BP0YyjRofWCeRyfplJJ6MhbaJ2xGRkEVzKV9GtFFXqob8NG98yXKOUafvhem4CZAldkB94Wy9saC-pnxElhWvfwxfDPpKJP7h8/s1600/img4.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="295" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLbahiysrBBDBs_wEQfCyQPxcvYukSN_3UKCDfN3Geg1BP0YyjRofWCeRyfplJJ6MhbaJ2xGRkEVzKV9GtFFXqob8NG98yXKOUafvhem4CZAldkB94Wy9saC-pnxElhWvfwxfDPpKJP7h8/s400/img4.PNG" width="400" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;"><br /></span></div> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;">Procedure</span></b><span style="font-size: 14.0pt; line-height: 115%;">- A loopful from a broth or agar plate is taken into a glass slide. Then the smear is prepared by heat fixing at bunson flame. As the proteins of the cell wall are denatured by heat, it supports the bacterium cells to adhere to the slide. The smear is stained by flooding with Malachite green. It is allowed Malachite green to act for 5 minutes.  The underside of the slide is heated by using alcohol deep cotton wool.  It is allowed the slide to cool. Stained smear is decolorized by using water and air dry. Safranin is added as the counterstain. It is allowed Safranin to react for 30seconds. Excess Safranin is washed away by using water and air dry. Endospore and it vegetative cell are observed under oil immersion objectives.<o:p></o:p></span></div> <div class="MsoNormal"> <br /></div> <div class="MsoNormal"> <br /></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%; mso-no-proof: yes;"> </span></div> <div class="MsoNormal"> <b><u><span style="font-size: 14.0pt; line-height: 115%;">Observations:<o:p></o:p></span></u></b></div> <div class="MsoNormal"> <b><u><span style="font-size: 14.0pt; line-height: 115%;"><br /></span></u></b></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDemc-USk1p5gBO5BwBzy9iQmWlZdF8a_2hR37CnFJqSg7dDCW2XxYrGoAwC4gLhxtQ04_5FoLgF_FA6kBJwj-S_la0KuQX6qE1Q_maboQjag7LIhm9rDz7bkQTkwbGthc82ToD6AOh4EN/s1600/img5.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="297" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDemc-USk1p5gBO5BwBzy9iQmWlZdF8a_2hR37CnFJqSg7dDCW2XxYrGoAwC4gLhxtQ04_5FoLgF_FA6kBJwj-S_la0KuQX6qE1Q_maboQjag7LIhm9rDz7bkQTkwbGthc82ToD6AOh4EN/s400/img5.PNG" width="400" /></a></div> <div class="separator" style="clear: both; text-align: center;"> <br /></div> <div class="MsoNormal" style="margin-left: .25in;"> <b><span style="font-size: 14.0pt; line-height: 115%;">Theory</span></b><span style="font-size: 14.0pt; line-height: 115%;">:<o:p></o:p></span></div> <div class="MsoListParagraphCxSpFirst" style="margin-left: .75in; mso-add-space: auto; mso-list: l0 level1 lfo1; text-indent: -.25in;"> <!--[if !supportLists]--><span style="font-size: 14.0pt; line-height: 115%; mso-bidi-font-family: Calibri; mso-bidi-theme-font: minor-latin;">1)<span style="font-size: 7pt; font-stretch: normal; font-variant-numeric: normal; line-height: normal;">    </span></span><!--[endif]--><span style="font-size: 14.0pt; line-height: 115%;">At the room temperature, the spore wall which mostly contain keratin resist to dyes. But heating make the spore wall more permeable to malachite green and allow it to bind to peptidoglycan layer. <o:p></o:p></span></div> <div class="MsoListParagraphCxSpMiddle" style="margin-left: .75in; mso-add-space: auto; mso-list: l0 level1 lfo1; text-indent: -.25in;"> <!--[if !supportLists]--><span style="font-size: 14.0pt; line-height: 115%; mso-bidi-font-family: Calibri; mso-bidi-theme-font: minor-latin;">2)<span style="font-size: 7pt; font-stretch: normal; font-variant-numeric: normal; line-height: normal;">    </span></span><!--[endif]--><span style="font-size: 14.0pt; line-height: 115%;">So both vegetative cell and endospore are stained in green color.<o:p></o:p></span></div> <div class="MsoListParagraphCxSpMiddle" style="margin-left: .75in; mso-add-space: auto; mso-list: l0 level1 lfo1; text-indent: -.25in;"> <!--[if !supportLists]--><span style="font-size: 14.0pt; line-height: 115%; mso-bidi-font-family: Calibri; mso-bidi-theme-font: minor-latin;">3)<span style="font-size: 7pt; font-stretch: normal; font-variant-numeric: normal; line-height: normal;">    </span></span><!--[endif]--><span style="font-size: 14.0pt; line-height: 115%;">After cooling, spore wall seals again and trap malachite green inside the wall.<o:p></o:p></span></div> <div class="MsoListParagraphCxSpMiddle" style="margin-left: .75in; mso-add-space: auto; mso-list: l0 level1 lfo1; text-indent: -.25in;"> <!--[if !supportLists]--><span style="font-size: 14.0pt; line-height: 115%; mso-bidi-font-family: Calibri; mso-bidi-theme-font: minor-latin;">4)<span style="font-size: 7pt; font-stretch: normal; font-variant-numeric: normal; line-height: normal;">    </span></span><!--[endif]--><span style="font-size: 14.0pt; line-height: 115%;">At the decolonization step, malachite green rinse only forms the vegetative cells. <o:p></o:p></span></div> <div class="separator" style="clear: both; text-align: center;"> </div> <div class="MsoListParagraphCxSpLast" style="margin-left: .75in; mso-add-space: auto; mso-list: l0 level1 lfo1; text-indent: -.25in;"> <!--[if !supportLists]--><span style="font-size: 14.0pt; line-height: 115%; mso-bidi-font-family: Calibri; mso-bidi-theme-font: minor-latin;">5)<span style="font-size: 7pt; font-stretch: normal; font-variant-numeric: normal; line-height: normal;">    </span></span><!--[endif]--><span style="font-size: 14.0pt; line-height: 115%;">Counter stain, safranin I only able to stain the vegetative cell because stain is unable to penetrate the spore wall due to the less permeability. <o:p></o:p></span></div> <div class="MsoNormal"> <br /></div> <div class="MsoNormal"> <b><u><span style="font-size: 14.0pt; line-height: 115%;"><br /></span></u></b></div> <div class="MsoNormal"> <b><u><span style="font-size: 14.0pt; line-height: 115%;"><br /></span></u></b></div>

Endospore staining

Endospore is domanet strucure which have no or less metabolic activities. Bactiers form endospre when environemntal conditions are  unfavo...

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Wastewater treatment

<div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">Wastewater contains a large fraction of organic matter which needs to be treated before discharge. Aerobic respiratory bacteria are capable of degrading organic matter into carbon dioxide and water in the presence of the oxygen.  It leaves environment clean without any residue. But the action of aerobic respiratory bacteria is inhibited when there is no adequate oxygen.  <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Then anaerobic respiratory bacteria become active. They are also able to degrade organic matter into carbon dioxide. But they use non oxygen terminal electron acceptors such as sulfate, ferric and nitrate ions. They reduce sulfate ions into odiferous toxic gas hydrogen sulfide, water insoluble ferric into ferrous and nitrate into nitrogen gas which cause infertility in aquatic ecosystems. So although anaerobic respiratory bacteria degrade organic matter completely into carbon dioxide, they cause environmental pollution. <o:p></o:p></span></div> <div class="MsoNormal">                                        <span style="font-size: 14.0pt; line-height: 115%;">Under anaerobic conditions, fermentation also takes place. Fermentative bacteria such as <b><i>Clostridium</i></b> use organic matter as their substrate and degrade them partially into acids, alcohols and aldehydes. Acids cause acidification of aquatic water bodies. Acids dissolve minerals and release toxic metal ions to the water. Ex: Al (3+). Alcohols and aldehydes may be volatile which cause atmospheric pollution. They cause producing unpleasant odor. If enough oxygen is available, these small organic compounds can be degraded into carbon dioxide completely.  But in most cases oxygen is still not available, so anaerobic respiratory microorganisms degrade these small organic compounds into carbon dioxide and cause pollution. <o:p></o:p></span></div> <br /> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                             Therefore anaerobic respiration and fermentation are not the proper solutions for wastewater treatment. <b>Aerobic respiration is the best solution</b>. Wastewater is collected from the all over the premises and directed into an aeration tank. Here water is continuously aerated for 4-8 hours. Mechanical aerators are used to oxygenate the water. The oxygen concentration should be maintained in-between 0.5-2mg/l. it is impossible to retain wastewater until the all organic matter degrade.  After retention time, wastewater is transferred to the settling tank or primary clarifier. Here unoxidized or partially oxidized organic matter is allowed to settle down at the bottom while clear water is directed for further treatment.  A fraction of sediments is returned to the aeration tank as the <b>activated sludge</b> to enhance the treatment process.</span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEheabdBYImTAxJGToq8uWevte7xJwJ0dMkhaUI5wjlMbr2ZOEEKhx-hSDTyF8w1hD6fjl2JKlOggPYM-qwItXzfCX4UlPRx4cEkTLSNpgLEeOa9ABNxhVPKn_1anQiKVnljzPhfC6_h8pgP/s1600/wastewater.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="302" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEheabdBYImTAxJGToq8uWevte7xJwJ0dMkhaUI5wjlMbr2ZOEEKhx-hSDTyF8w1hD6fjl2JKlOggPYM-qwItXzfCX4UlPRx4cEkTLSNpgLEeOa9ABNxhVPKn_1anQiKVnljzPhfC6_h8pgP/s640/wastewater.jpg" width="640" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><b><span style="font-size: 14.0pt; line-height: 115%;">Sludge digestion</span></b><span style="font-size: 14pt; line-height: 115%;">: The sediment that is collected from the bottom of settling or sedimentation tank is transferred into an anaerobic digester. Sludge is completely degraded into carbon dioxide. The sludge mostly contains the high strength organic matter which is needed to degreed into small organic compounds by fermentative bacteria such as <b><i>Clostridium. </i></b>They degrade the organic matter partially into acids, alcohol and aldehydes. Then small organic compounds are degraded completely into carbon dioxide by anaerobic bacteria. Most of that carbon dioxide is reduced into Methane by methanogens such as <b><i>Methanomonas </i></b>and <b><i>Methanococcus</i></b>. Methane is a combustible gas which can be used as alternative fuel for fossil fuel. The reaming in the digester is transferred into another setting tank for settling down for sediments. A portion of this sediment is returned to the digester for seedling the incoming unoxidized sediments. Rest is disposed as a valuable fertilizer for agriculture and land escaping.</span> <o:p></o:p></span></div>

Wastewater treatment

Wastewater contains a large fraction of organic matter which needs to be treated before discharge. Aerobic respiratory bacteria are capable...

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Gram staining

<div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;">Gram staining</span></b><span style="font-size: 14.0pt; line-height: 115%;"> is a differentiate staining technique which is used to differentiate bacteria into two groups such as gram positive and gram negative based on their ability to retain color during staining. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              <b>Gram negative bacteria </b>have outer lipid membrane which surrounds the cell membrane. Only 10% of their cell wall is comprised of peptidoglycan.  Ex: Salmonella, Shigella, Escherichia coli (E. coli). Gram negative bacteria are stained in pink color. <o:p></o:p></span></div> <br /> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                          <b>Gram positive bacteria</b> have no outer lipid membrane. 80-90% of their cell wall is comprised of peptidoglycan.</span> <span style="font-size: 14.0pt; line-height: 115%;">Ex:  Bacillus, Clostridium, Lactobacillus, Listeria, Taphylococcus, Streptococcus, and Streptomyces. Gram positive bacteria are stained in purple color.</span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_lf0Anc4uytW1a1-wjv6YD8VlCAjBmtSA4YGe0P91z4H_gPBYNQuUGxEsqn61L_0FearGAlwsCM2W-TcUes8qCaR_WACc4hAGvw2E75f_NxkxQEQCO6ap0aFwMu4DywA-aFgQq5QJ4ZLg/s1600/img1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="198" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_lf0Anc4uytW1a1-wjv6YD8VlCAjBmtSA4YGe0P91z4H_gPBYNQuUGxEsqn61L_0FearGAlwsCM2W-TcUes8qCaR_WACc4hAGvw2E75f_NxkxQEQCO6ap0aFwMu4DywA-aFgQq5QJ4ZLg/s320/img1.jpg" width="320" /></a></div> <br /> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;">Procedure-</span></b><span style="font-size: 14.0pt; line-height: 115%;"> A loopful from a broth or agar plate is taken into a glass slide. Then the smear is prepared by heat fixing at bunson flame. As the proteins of the cell wall are denatured by heat, it supports the bacterium cells to adhere to the slide. The smear is stained by flooding with crystal violet. It is allowed crystal violet to react with smear for 2 minutes. Gram’s iodine is added to from large Crystal violet iodine complex. It is allowed iodine to react for 1minutes. Excess</span> <span style="font-size: 14.0pt; line-height: 115%;">Crystal violet iodine complex is drained from the slide.  The smear is decolorized by adding 95% ethyl alcohol without washing for 3o seconds. The stain from the cell wall is rinsed by water. Safarin is added as the counterstain. It is allowed safarin to react with smear for 30 seconds. It is rinsed by water and allows air dry. The stained smear is observed under dry high, mid or lower power objectives or oil immersion objectives. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><b><u><span style="font-size: 20.0pt; line-height: 115%;">Observations:</span></u></b></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj7BpvIXmlyHjxRj2y2F-h8JufzKPMb0i-uAgQf7YGWDe5SlZyQU6g7Hw637SKpJi6GNIyS_cbreo-I_rCF30aqzg8UqaWL-qO8MXKCAbtirmVHDgyiYTT608PVAbyXKGQ0cVcvcEtc02Ip/s1600/img2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="313" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj7BpvIXmlyHjxRj2y2F-h8JufzKPMb0i-uAgQf7YGWDe5SlZyQU6g7Hw637SKpJi6GNIyS_cbreo-I_rCF30aqzg8UqaWL-qO8MXKCAbtirmVHDgyiYTT608PVAbyXKGQ0cVcvcEtc02Ip/s320/img2.jpg" width="320" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;">Crystal violet</span></b><span style="font-size: 14.0pt; line-height: 115%;">- Crystal violet is added as the primary stain. It is a basic stain. Its positively charged ions penetrate the cell walls of both gram positive and gram negative and bond to the negatively charged cell components. So both gram positive and gram negative cells are stained in purple color. <o:p></o:p></span></div> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;">Gram’s Iodine</span></b><span style="font-size: 14.0pt; line-height: 115%;">- It is added as the mordant. It increases the affinity of ions of the primary stains to cell wall via reaction with crystal violet ions. It forms large Crystal violet iodine complex. Both gram positive and gram negative cells are still stained in purple color.<o:p></o:p></span></div> <div class="MsoNormal"> <b><span style="font-size: 14.0pt; line-height: 115%;">95% Ethyl alcohol</span></b><span style="font-size: 14.0pt; line-height: 115%;">- In the case of gram negative bacteria, ethyl alcohol is able to dissolve the outer lipid membrane. It left the cell membrane exposure. It increases the porosity of the cell wall. So after addition of 95% Ethyl alcohol, water is able to wash away large Crystal violet iodine complex from the thin peptidoglycan layer.  So after water resining, the smear appears in colorless.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                    Ethyl alcohol acts as dehydrate agent in gram positive bacteria. It causes the pores in the cell wall to shrink. So water is unable to wash away large Crystal violet iodine complex from the thick peptidoglycan layer. So after water resining, the smear still remain in purple color. <o:p></o:p></span></div> <div class="MsoNormal"> <br /></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><b><span style="font-size: 14.0pt; line-height: 115%;">Safranin</span></b><span style="font-size: 14pt; line-height: 115%;">- Safranin is added as counter stain. Gram negative bacteria appear in pink color. Gram negative bacteria are unable to stain in safranin and still appear in purple color.</span> <o:p></o:p></span></div>

Gram staining

Gram staining is a differentiate staining technique which is used to differentiate bacteria into two groups such as gram positive and gram...

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Sterilization Techniques in Microbiology Laboratory

<div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhy8eT7M86oVS9ux8lbWCsVXy_dGZ2VQl_9Sj-EC0XfjE8AR2QmfYMiUN_NehpEDcsgvfmymeCX1qbYiyY44ywHQwfc208wJYFru7qD6eByEDCnW-LjyIyHo-Pteh4cEgKYfsKuRqM-GRHw/s1600/sterilization.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="360" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhy8eT7M86oVS9ux8lbWCsVXy_dGZ2VQl_9Sj-EC0XfjE8AR2QmfYMiUN_NehpEDcsgvfmymeCX1qbYiyY44ywHQwfc208wJYFru7qD6eByEDCnW-LjyIyHo-Pteh4cEgKYfsKuRqM-GRHw/s640/sterilization.jpg" width="640" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">Sterilization is destruction of all microorganisms and their spores from the surface of equipment and from certain environments. Sterilization is essential in microbiology laboratory to carry out testing in the microorganism’s free environment because unwanted or untargeted microorganisms can be contaminated with testing. It may give wrong results which leads to make wrong decisions. As an example, if the culture media where there is no gram positive is contaminated with gram positive bacteria, it give positive  results which require further testing for confirm. After usage, culture media must be sterilized before disposal into the environment because culture media contain thousands of microorganisms. The situation become serious, when the culture media contains pathogens which causes extremely health risks. Sterilization techniques are important for the health protection of working people in the microbiology laboratory. Because when they handle pathogenic microorganisms, there is a high probability to infect the people who have low immunity. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Several sterilization techniques are available in microbiology laboratory such as heat sterilization, radiation and filtration. Combinations of these approached are used to achieve better sterilization rather than one approaches. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Heat sterilization is physical sterilization techniques. The period of heating or temperature of heat can be increased to achieve better sterilization. Moist heat or dry heat can be used. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Under moist heat, two methods are available such as boiling and autoclave. In boiling technique, equipment are just boiled at 100◦C. Boiling is only capable of killing microorganisms. It fails to kill their spores. So it is only used when other methods are not available. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Autoclave uses steam to kill microorganism. It is able to kill both microorganisms and their spores. It produces steam at elevated temperature and elevated pressure. Steam penetrates the equipment’s surfaces and sterilizes them.  It is operated either at 115◦C for 60 minutes or at 121◦C for 40 minutes at 15 ibs/sq. It is used to sterilize glassware and culture media. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Moist heat method has some advantages as well as disadvantages.it does not use toxic material or chemicals. It is expensive. It is highly effective because steam penetrates rapidly the equipment. It cannot be used for sterilization of thermo unstable substances. After sterilization, autoclave left some moisture on the surface of the equipment. It causes the corrosion. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              In dry heat, three methods are available such as flaming, hot air oven and alcohol dip. Equipments are flaming directly at bunson flame until red hot. Metallic equipment such as loop and needles are sterilized by flaming directory at buson flame. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Hot air oven use hot air to sterilize. The heat is evenly distributed throughout the oven by using conventional current. Sterilization is applied in the hot air oven at 115◦C for 60 minutes for one hour period. For better sterilization, either temperature can be increased to 160◦C or the period of the heat can be increased to 2-3 hours. Hot air oven is used to sterilize glass equipment such as petri dishes, flasks and pipettes. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              After dipping in alcohol, equipment is directly flamed directly in bunson flame. It kills fungi, bacteria and viruses via dissolving their cell membranes.  Glass equipment such as glass spreader and glass rod are sterilized by using dip alcohol. Alcohol is also used to swab the lab bench top. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Use of dry heat is also nontoxic. It has low operation cost and easy to install. It is non-corrosive. It is time consuming because it slowly penetrates the equipment than steam does. It cannot be also used for sterilization of thermo unstable substances.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Two types of radiations are available for sterilization such as ionizing and non-ionizing radiation. Ionizing radiation uses the short wave length and high intensity radiation. It kills the microbe via reaction with their nuclei. ɤ rays and x rays are used for ionizing radiation. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Non-ionizing radiation involve the use of long wave length and low intensity radiation. UV rays are used for non-ionizing radiation. It is impossible to penetrate equipment. Therefore it is only used for sterilize surfaces such as lab bench top. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Radiation sterilization is reliable. It does not leave any chemical residues. It can be used to sterilize thermo unstable substances. It is expensive techniques. It requires highly specialized equipment. It is harmful to workers when work with radiation for long time and exposure to radiation in high dose. It is not only killing the microorganisms but it also destroys the properties of media. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Filtration sterilization allows the microorganisms to separate based on their size. Membrane filtration, Hamming’s filtration and syringe filtration are used for filtration sterilization. Membrane filtration use membrane to spate microorganisms. The microorganisms that are larger than the pore size are trapped on the surface of the membrane. The microorganisms that are too small than pore size can pass through the membrane. Therefore with the decreasing size of the microorganisms, the pore size is also reduced.  Usually membrane with pore size 0.04µm or below 0.04µm is used. Vacuum is used to increase efficiency of the filtration. Hamming’s filtration is used to filter low volumes. Syringe filtration is used to filter even least volumes. Here pressure is applied to achieve better filtration. Vacuum is not used in both Hamming’s filtration and syringe filtration.<o:p></o:p></span></div> <br /> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                              Filtration sterilization is used to sterilize thermo unstable substances such as culture media, enzymes, vitamins and antibodies. It filters large volumes more rapidly. It helps to separate microorganisms based on their size. It is inexpensive. The smallest microorganisms are able to pass through the membrane. Membrane absorbs significant volume of filtrate. It is impossible to separate two microorganism species with same size.<o:p></o:p></span></div>

Sterilization Techniques in Microbiology Laboratory

Sterilization is destruction of all microorganisms and their spores from the surface of equipment and from certain environments. Ster...

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Angiosperm lifecycle

<div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMdHEqWzrvLWP3cMNTO3VkkS-h_4tY6Gp7OsaqzlxM6ZxwvaImCBg0RkELcwnSnPC6gLNV7MCWh0fHeEYBvYGUpDeUg2FBFRGCnKjnkkKvCkYXGh3pRNxjNnkufbQ1d2Tw3sIe8MJ-cgkU/s1600/Image1.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMdHEqWzrvLWP3cMNTO3VkkS-h_4tY6Gp7OsaqzlxM6ZxwvaImCBg0RkELcwnSnPC6gLNV7MCWh0fHeEYBvYGUpDeUg2FBFRGCnKjnkkKvCkYXGh3pRNxjNnkufbQ1d2Tw3sIe8MJ-cgkU/s640/Image1.gif" width="640" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">Angiosperms have been evolved 130 million years ago in the earth. They are most dominating plant form in the present.  Angiosperms are categorized into three groups such as monocots, eudicots and basal angiosperms. Earlier both eudicots and basal angiosperms are collectively called as dicots. Basal angiosperms show most evolutionary primitive characters. Compositae (daisies) from eudicots, and Orchids from monocots are evolved with most advanced characters. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                Flowers are the reproductive structure of angiosperms. They are considered as modified strobilus.  Female part of flower is carpel. The carpel is comprised of three parts such as stigma, style and ovary.  Stigma receives pollen grains coming from a stamen. Style connects the stigma to ovary.  Ovary protects the ovules. After fertilization, ovary becomes fruit wall.  Ovules become seeds.  Stamen is the male part of flower. It consists of two parts such as anther and filament. Anther produces pollen grain.  Filament bears the anther. Some species produce flowers bears both female and male parts. This kind of flowers is called as <b>bisexual</b>. Rose produces bisexual flowers.  Some species produce flowers bear only female part of male part. Such flowers are called as <b>unisexual</b>. Coconut, papaya and pumpkin are the example for producing unisexual flowers.   Those carpel and stamen are the fertile parts of the plants. Fertile parts of flowers are covered by infertile parts such as sepals and petals. Sepals protect the inner parts of the flower. Petals which are often in bright colures and large size attract pollinators. Some flowers and their associated pollinators are coevolved.  The evolutionary change in the plants causes the evolutionary change in pollinators too. Pollinators help to disperse the pollen grain into further distance. They help to develop new gene combinations. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                Fertilization of angiosperms refers to as the deposition of pollen grain from an anther on a stigma. Pollen grains may come from a stamen of either same flower or another flower in same tree or flower in another tree.  <b>Self-fertilization</b> refers to as the deposition of pollen grain from an anther of same flower on the stigma. <b>Cross fertilization</b> refers to as the deposition of pollen grain from an anther of another flower on same tree or of another flower on another tree on a stigma. Most of angiosperms are evolved to prevent self-fertilization. Stigma gets mature earlier than anther. Stamen may shorter or longer than stigma. Unisexual flowers are best adaptation to avoid self-fertilization in flowers. Cross fertilization help to develop new gene combinations and enhance the present gene pool of plant. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                Angiosperms produce neither archegonia nor antheridia. They produce ovule and pollen grains. Pollen grains are the partially developed male gametophyte. The diploid microsporocyte(microspore mother cell) undergoes meiosis and produce haploid microspores. Those microspores undergo mitosis and develop into pollen grains.  . It bears two cells such tube cell and generative cell. The pollen grains may deposit on the stigma via animals, water or wind. Pollen grains may disperse via animals when then contains reward for pollinators. Pollen grain can be dispersed by wind or water when they are light weight, have winds like structures or produce in large quantity.  <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                Inside ovary, ovules are produced. The diploid megasporocyte (megaospore mother cell)  undergo meiosis and produce four haploid megaspores. Three megaspores are degenerated. Only one megaspore survives. Later it becomes functional megaspore. It undergoes there rounds of mitotic cell division. It results in seven cells and eight nuclei with only seven cytokinesis. The endosperm mother cell contains two nuclei. Those nuclei are called as polar nuclei. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                        After deposition of pollen grain on a stigma, Generative cell produces two sperm. Tube cell develop into large pollen tube. The pollen tube penetrates the stigma and enters through the style into ovule. The sperm are conveyed through the pollen tube. Angiosperms have evolved with another evolutionary advanced feature such as <b>double fertilization</b>. One of sperm fertilizes the egg cell and produce diploid zygote. The zygote divides several time and produce multicellular embryo. Other sperm fertilize the polar nuclei and form triploid endosperms. T The endosperm provides nutrients for developing embryo. Eventually the developing embryo and endosperm are enclosed in a seed. Ovules develop into seed. Ovary wall develops into the fruit. <o:p></o:p></span></div> <br /> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                        Angiosperms also have seed dispersal animals. The fruits which have not edible part are adopted to disperse their seeds in winds, water or attach to animals. Some fruits are borne with hooks or spine to attach to animal fur<b>. Ex: <i>Achyranthes aspera</i></b>. Some fruits are associated with wind like structures to disperse their seeds via wind. <b>Ex:</b></span><b> </b><b><i><span style="font-size: 14.0pt; line-height: 115%;">Dipterocarpus zelanicaus</span></i></b><span style="font-size: 14.0pt; line-height: 115%;">.  Enclosing seed in a fruit helps to disperse into further area via animals. It helps angiosperms to colonize new area.  Seed have long life span than spores. Seed coat is thicker resist against pest attack and mechanical damage.<o:p></o:p></span></div>

Angiosperm lifecycle

Angiosperms have been evolved 130 million years ago in the earth. They are most dominating plant form in the present.  Angiosperms are ...

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Gnetophyta (Gnetophytes)

<div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbH5FQX3ktfl-6pwpHu04Dhv5eKiGQsWqTYNY2PaDW4Ju1NPe8P9EjiBllG9vYN0HpLVV3oxTPmX2tbDdHL-NlEfHXenAAnB-Szc368Ql99JJsTRz8ks5kwEQBYkkG7yGSp333W7-Ggt00/s1600/img1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="385" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbH5FQX3ktfl-6pwpHu04Dhv5eKiGQsWqTYNY2PaDW4Ju1NPe8P9EjiBllG9vYN0HpLVV3oxTPmX2tbDdHL-NlEfHXenAAnB-Szc368Ql99JJsTRz8ks5kwEQBYkkG7yGSp333W7-Ggt00/s640/img1.jpg" width="640" /></a></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;"><br /></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">Gnetophytes are considered as the evolutionary link between gymnosperms and angiosperms. Today only there genera represents the Gnetophytes such as <i>Welwitshchia, Gnetum</i> and <i>Ephedra</i>.  These there genera differ greatly from one another in form, structure and function. From those three genera, <i>Welwitschia</i> and <i>Gnetum</i> show evolutionary closer relationship to angiosperm.  <i>Ephedra</i> is evolutionary more closely to gymnosperms. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                             .  Gnetophytes are the only gymnosperms who have vessels in the secondary xylem as in angiosperm. Vessels are relatively efficient water and minerals conducting cell type. The size of gametophyte generation is further reduced. Sporophyte generation becomes further dominant.  Their sperm is non-motile. They possess separate female and male strobilus. Their seeds are comprised of two integuments. Inner integument exudes pollen droplets which draws the pollen grain to ovule. Outer integument is not a true one. Pollen tube of Gnetophytes is siphonogamous. Their pollen tube conveys their sperm directly to the archegonia of <i>Ephedra</i> or female gametophyte in Welwitschia and Gnetum. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                   <i>Ephedra</i> is the most primitive form of Gnetophytes. It inhabits in arid zones and sandy places.  It is a highly branched shrub.  It has a jointed stem with whorls of tiny scale like leaves at each node.  Depending on the species some are monoecious while some are dioecious.  Their pollen grains have sterile cells. They possess archegonia. Its female gametophyte has monosporic development.  Free nuclei division without cell wall accompanying is present in female gametophyte formation. Their female cone is resembled as brightly colored berrylike fleshy structures.  Their male cone is appeared as spike like clusters.<o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                                   <i>Welwitschia </i>possess a ring shape stem. It anchors to the soil aid in huge taproot with surface roots. Its leathery leaves rise up from the stem and continue the growth. It bears reproductive structures which rise at the base of the stem. They produce separate female and male plants.  Sterile cells are absent in the pollen grains of Welwitschia. Its female gametophyte has tertasporic origin. Archegonia are entirely absent. It has free nuclei period in embryogenesis. Pollen cones and ovulate cones are produced in separate plants.  They are borne at the end of the branched systems of plants. Insects are attracted to pollinate the pollen grains by secreting nectar. Only one seed is produced per a cone. Seeds bears fly like structures in order to disperse them aid in wind. <o:p></o:p></span></div> <div class="MsoNormal"> <span style="font-size: 14.0pt; line-height: 115%;">                               Although <i>Gnetum</i> and <i>Welwitschia</i> share common characters, only <i>Gnetum</i> has been proposed as the probable ancestor of Angiosperms because distribution of Welwitschia is restricted to desserts. But <i>Gnetum</i> is widely distributed all over the world. <o:p></o:p></span></div> <br /> <div align="center" class="MsoNormal" style="tab-stops: 105.75pt; text-align: center;"> <i><span style="font-size: 14.0pt; line-height: 115%;">                               Gnetum</span></i><span style="font-size: 14.0pt; line-height: 115%;"> successfully grow in humid and tropical regions. Most species of <i>Gnetum</i> are in the form of climber. Some species are in the form of shrubs and trees. They possess complex microsporangiate and megasporangiate cones. They are similar in inflorescences in the angiosperms. They bear board leaves which are similar in form, structure and venation to those found in Eudicots of angiosperms.</span> <span style="font-size: 14.0pt; line-height: 115%;">They secret nectar which attracts insects for their pollination. Their seeds are enclosed in a false fruit.  It helps to disperse their seed aid in animals. Archegonia are entirely absent. Their pollen grains are lack of sterile cells. They only carry generative cells which produce two sperm cells and tube cells which produce large tube cells. Their female gametophyte is formed as a result of tertasporic development. In both <i>Welwitschia</i> and <i>Gnetum</i>, female gametophyte formation is associated with free nuclei division without accompanying cell wall accompanying formation. <o:p></o:p></span></div>

Gnetophyta (Gnetophytes)

Gnetophytes are considered as the evolutionary link between gymnosperms and angiosperms. Today only there genera represents the Gnetoph...

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