Microbiology Unknown

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Autumn White Biology 258-05 November 26, 2012 Unknown #19 Enterbacteriaceae Enterobacter aerogenes ABSTRACT The objective of this report was to identify an unknown microorganism through several differential media tests. Over the course of a couple weeks, ten tests were performed. First, a gram stain was performed, indicating the bacterium was gram negative. An aerotolerance test determined that the bacterium was a facultative anaerobe. Next, a negative result in the methyl red test indicated that no mixed acid fermentation occurred. The DNase test was performed and yielded a positive result. The SIM test provided two outcomes, that the bacterium did not reduce sulfur nor produce indole from tryptophan.…show more content…
After incubation, approximately 6-8 drops of methyl red were added Possible observations: If mixed acid fermentation occurs, the broth will turn red. If mixed acid fermentation does not occur, the broth will not change its color. DNase Test 1. The bacterium was inoculated with a flamed loop onto agar containing peptides for soybeans, casein, NaCl and DNA 2. The plate was incubated at 37C for 24 hours Possible observations: If there is a clearing in the agar around the growth, then DNase is present. If there is not a clearing in the agar, DNase is not present. SIM Test: Tests for sulfur reduction, indole production from tryptophan, and motility 1. The SIM slant was stabbed with a flamed needle inoculated with the bacterium 2. The slant was incubated at 37C for 24 hours 3. After incubation, Kovacs’ reagent was added. The Kovacs’ reagent will react with any indole present Possible observations: If sulfur was reduced, there will be black in the medium. If sulfur was not reduced, there will not be black in the medium. If tryptophan is broken down into indole and pyruvate, there will be red in the alcohol layer of Kovacs’ reagent. If tryptophan does not break down, then the reagent color will be unchanged. If there is growth radiating from the stab line, there is motility. If there is no radiating growth, there is no motility. Lysine Decarboxylase: Tests for the presence of lysine decarboxylase, which breaks down an amino acid, and glucose
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