Essay on Micro Unknown Lab Report

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| Gram Negative Unknown | Biology 3444-006 | | Lena Wallace | 11/7/2011 |


The purpose of this lab was to identify an unknown bacteria culture using differential tests. The identification of the unknown culture was accomplished by identifying the bacteria based on its specific metabolic characteristics and morphology. It is suggested that culture 11 is a sample of Enterobacter aerogenes.
This experiment was centered on metabolic and biochemical testing procedures. The rationale of performing these tests was to distinguish six different microbes from one another and to compare how their metabolic and biochemical processes differ from species to species to determine the unknown sample.
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If the broth turns yellow, it means that acid was produced and reported as A. If the organism can break down the amino acids be de-amination and ammonia is produced, this will raise the pH level turning it pink. This alkaline result was reported as K.
The Methyl Red test is a differential test for bacterial respiration used to differentiate strains of coliform bacteria capable of performing mixed acid fermentation that will lower the pH despite the phosphate buffer ( Mixed acid fermentation is confirmed by using methyl red as an indicator. It is red ant pH 4.4 and below, yellow at pH 6.2 and above, and orange in between. Red is a positive result reported as (+), yellow is a negative result reported as (-), and orange is negative or inconclusive.
The Voges-Proskauer test to detect organisms that are able to ferment glucose, but convert the products to acetoin and 2,3-butanediol. This is deduced by the addition of Reagent A and Reagent B, and the observation of the color change thereafter. Reagent A is a solution of -naphthol and alcohol. Reagent A catalyzes the conversion of acetoin to diacetyl. Diacetyl thens react with guanidine-containing compounds from the peptone to form a red color in the presence of -naphthol. Reagent B is a solution of potassium hydroxide and water. It
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