Unknown Lab Report

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Abstract: In lab, we were given the broth of an unknown bacteria labeled with simply a number. The purpose of this experiment, is to use the techniques previously acquired during the course of the lab in order to identify the unknown. The unknown presented will be one of three gram-negative bacteria: Escherichia coli, Klebsiella pneumoniae, or Salmonella typhimurium. The streak plate technique and Gram Staining methods were completed in order to obtain colonies and to identify the morphology of the unknown bacteria, respectively. As each class of bacteria has strict metabolic requirements and living characteristics, the unknown bacterium was differentiated and identified through a series of biochemical tests. After performing the tests on the…show more content…
aureus. The citrate test and EMB plate were definitive assurances of the unknown gram negative bacterium K. pneumoniae. Comparing the results to the characteristics on the chart given, S. aureus is the only bacteria with positive coagulase test and an acid producer on the MSA plate. Since citrate and SIM were among the few tests that were completed in 24 hours, the suspicions for the bacteria being S. aureus came fairly early in the experiment. The remainder of the tests were used primarily to confirm the suspicions. SFA and catalase tests were not among the tests used to identify the bacteria due to the similarity of the results found in the other bacteria. The positive bile esculin test and gram staining helped to rule out the remaining bacteria on the chart. For the gram negative, K. pneumoniae and E. coli were the only 2 bacteria to produce metallic green results on the EMB plates. This test allowed me to narrow it down to just 2 bacteria. TSIA, MR, VP, and MacConkey did not help rule out a particular bacteria, as they all have the same conclusive results. Although, the SIM, citrate, and urease were all confirmation of the unknown bacterium to be K. pneumoniae, the citrate test was upon the first to be completed and observed giving it the test to be the deciding factor. The other two tests were just confirmations. All of the tests matched exactly with the results given on the

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