Rod shape, gram- and oxidase-negative, and glucose-positive are defining characteristics of Enterobacteriaceae (Rollins and Joseph).After limiting the probable species to family Enterobacteriaceae, the unknown bacteria were differentiated by the presence or absence of LDC. LDC is a member of a group of enzymes that breaks down amino acids by removing its carboxyl group (University of Arizona; Warren 17) Decarboxylase assays, together with H2S, VP, IND, and CIT, are the usual reactions utilized to identify Enterobacteriaceae down to their species level (Warren 17). Based on the LDC assay conducted, unknown A was tested positive for LDC, while unknown B tested negative. Enterobacter, Klebsiella, Escherichia and Salmonella are known for having LDC, while Proteus and Shigella are known not to have LDC (Warren 24-25). Out of the four LDC-positive genera, only Escherichia was VP- and CIT-negative, with the species E. coli being the most common. VP is another test for the ability to ferment carbohydrates (Warren 4), thus is used to verify the results obtained from the glucose test. On the other hand, CIT tests whether or not the bacteria in question is able to use citrate as a carbon source.After determining the identity of unknown A to be Escherichia coli, the LDC-negative unknown B was identified. Proteus and Shigella can be differentiated by the H2S assay, which detects whether or not the bacteria can generate H2S. Proteus is different from Shigella in that members of Proteus genus are able to synthesize H2S (Warren 43).The genus Proteus has two common species, P. mirabilis and P. They can be differentiated by means of IND. IND assay determines free indole molecules that came from deamination of tryptophan by typtophanase. Of the. Meaning of Bacteria.
Rollins, D. M. and Joseph S. W. “Enterobacteriaceae summary.” University of Maryland. 2000. http://www.life.umd.edu/classroom/bsci424/PathogenDescriptions/Enterobacteriaceae.htm. 11 August 2010.
“Lab 12: Microbial Metabolism (Part 2).” University of Arizona. http://microvet.arizona.edu/Courses/MIC205/Labs/Manual/12Microbial%20Metabolism2.htm. 11 August 2010.
“Methyl Red-Voges Proskauer (MRVP) Test.” Western Michigan University. https://homepages.wmich.edu/~rossbach/bios312/LabProcedures/MRVP%20Results.html. 11 August 2010.
Warren, J. R. “The Enterobacteriaceae Biochemical Properties.” Feinberg School of Medicine. pathology.northwestern.edu. 11 August 2010
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