Microbiology

Microbiology Study Guide

The third phase of the treatment is tertiary treatment, in which the output from the secondary treatment is further purified for extracting and removing phosphate and nitrate ions. In this case, the phosphate and nitrate ions are converted into solids by chemically combining them with calcium or iron. Then, with the help of the nitrification process, ammonia is released and the nitrates are oxidized. Further, activated charcoal is used to remove other chemical pollutants like polychlorinated biphenyls. Water Quality Tests It is possible to detect the presence of quantum and a variety of microorganisms in water using a number of water quality tests. This helps to detect and then keep the level of microbes and pollutants low in water supplies. Gene Probe Tests Gene probes are employed to test the water for the presence of bacteria. The main premise of this test is that the DNA particles of the gene probes unite with the complementary DNA fragments. The test is highly successful in detecting the presence of the bacteria Escherichia coli (gram-negative bacteria generally found in the intestine of human body) in water supplies. If the test detects the presence of these bacteria, it can be inferred that the water is contaminated with human feces, which is likely to have microbial pathogens. This test is conducted by adding the probe of Escherichia coli that searches for the presence of DNA of the bacteria. The presence of the bacteria is detected if the emissions of radioactivity are emitted. In the absence of radioactive emissions, it can be safely concluded that the bacteria Escherichia coli is not present in the tested water. The Membrane Filter Technique In this test, a membrane filter constituting a filtration apparatus and cellulose filter is used. The test is conducted by taking a sample of water and passing the same through the cellulose filter. Once the liquid has been passed, a filter pad is tested against the bacteriological growth medium, over which the trapped bacteria are multiplied to form colonies. These colonies are further counted and then one can make an estimate to learn the number of bacteria in the original sample. Therefore, this test is used to count the bacteria in water supplies. The Standard Plate Count It is important to note that it is not really possible to test and detect all the categories and number of microorganisms, but one can test the total count of bacteria with the help of the standard plate count test. In this test, a petri dish is used so that the water that needs to be tested is diluted in jars with sterile water and the nutrient medium or agar is added. The total bacteria count per ml of water is found by counting the bacteria colony in the sample and multiplying it with the dilution factor.

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