Water Testing and Differential of Enteric Bacteria

Water Testing and Differential of Enteric Bacteria - Water...

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Water Testing The purpose of the “Water Testing” lab is to understand the underlying principle of water testing and to be able analyze a water sample in order to verify whether or not coliforms are present; By conducting a series of tests to detect if the organism present in the water sample is aerobic (or facultative anaerobic), gram negative, non-endospore forming, rod shaped bacteria, that can ferment lactose with acid and produce gas (if it possesses these traits then it is a coliform). Coliforms are used as indicator organisms to detect fecal contamination in water. If a bacteria is aerobic or facultative anaerobic, gram negative, non-endospore forming, rod shaped, and is able to ferment lactose with acid and produce gas― it is an endospore. Two water sources used in the lab were water from Mirror Lake and Fenton River. The presumptive test uses lauryl- tryptose (LT) broth. LT broth contains lactose which supports coliform growth by fermentation, and gas production can be detected by the inverted durham tube. Both water samples tested showed positive results for gas production in the LT tubes. The confirmed test was conducted to tests whether or not the water samples from the positive presumptive tests are gram negative and whether they are lactose fermentors. The water samples were streaked onto the eosin-methylene blue agar, which contains a dye that inhibits the growth of gram positive organism and allow the growth of gram negative organisms. In addition, the agar differentiates lactose fermenters from
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Water Testing and Differential of Enteric Bacteria - Water...

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