Microbiology Lab Report Essay

2525 WordsSep 15, 201111 Pages
1. Title: The Process of Determining the Unknown Bacteria #9 Rachel Judecki July 5, 2011 2. Introduction: Each student was given unknown bacteria and was instructed to perform a variety of experimental tests that would help to identify their bacteria. During the process of identification, the unknown bacteria was added to many different testing medias using aseptic technique. They are as follows: lactose fermentation on eosin methylene blue (EMB), TSI (Triple Sugar Iron agar), Phenol red sucrose, the SIM test, H2S by SIM, IMViC (indole, motility, voges-proskauer, and citrate), Urease (urea broth), PDase (Phenylalanine Deaminase), Lysine Decarboxylase, and Ornithine Decarboxylase. Colonial morphology on EMB was used to…show more content…
Incubate the bacteria for about 24 hours and then begin testing. If hydrogen sulfide is present, it will react with the sodium thiosulfate in the medium and the indicator, ferric ammonium citrate, to produce ferrous sulfide which falls out of solution as a blackish precipitate. The presence of hydrogen sulfide typically means that the bacteria produces the enzyme cysteine desulfanase which breaks up the cysteine in the medium into hydrogen sulfide. A positive result will turn the medium black. If the result is negative then the medium will stay semi-clear. The unknown bacteria #9 produced negative results for H2S in the SIM test tube. The medium stayed semi-clear and did not turn black. IMViC reactions are a set of four reactions that are: Indole test, Methyl Red test, Voges Proskauer test and Citrate utilization test. The letter “i” is only for rhyming purpose. The Indole portion of the test is performed by adding Kovac's reagent to the inoculated SIM medium. The Kovac's reagent reacts with the indole (if indole is present) to produce a pinkish-red or reddish-purple ring around the top of the test tube. If indole isn't present, there will be no color change. The presence of indole indicates that the bacteria produces tryptophanase, an enzyme which breaks down tryptophan into smaller components, one of which being indole. The results for the indole test for unknown bacteria #9 were positive. When the

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