Part changes the color of broth from red

Part 2The experiment intended to apply all the techniques learned in the microbiology laboratory class to identify an unknown bacterium. After a series of tests, it was established that the bacterium of interests is Micrococcus leteus. After Gram staining the unknown bacterium, it was introduced to nutrient agar plates to provide colonies for further biochemical tests. The distinguishable feature of the genus Micrococcus from the rest of the genus is the microscopic observation of gram-positive cocci that are arranged in tetrads, pairs, or irregular clusters. In addition, the cocci are non-motile and non-sporing.

The use of Phenol Red Mannitol Broth was to establish if the unknown bacteria ferments mannitol, which is an acid that lowers the PH, which in turn changes the color of broth from red to yellow. Therefore, the unknown bacterium is not a mannitol fermenter. The utilization of the SIM agar is to determine if the unknown bacterium is enteric, motile, and is Enterobacteriaceae genus (Microbugz, n.d). It became apparent that bacterium in non-motile. The introduction of the bacterium to 15% NaCl tube is to determine if the unknown bacterium grows in different conditions, which are concentrated with salts. In this case, turbidity was observed in the test tube indicating that the bacterium grows in moderately saline conditions. Other distinctive features contributing to the identification of this bacterium include testing positive for catalase, gelatinase, glucose, and fructose tests.

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In addition, testing negative for citrate and lactose is another identifiable feature of the bacterium. By using the findings from these tests to constitute a dichotomous key, Micrococcus luteus was identified. In addition, the features were used to rule out other species. The Micrococcus genus is readily found in water, and on human skin as well as dust particles (Carter, 2017). However, the primary source is the mammalian skin (Michael et al., 2012, p.

574). .Rarely do Micrococcus leteus cause diseases in healthy individuals. For immunocompromised individuals, the bacterium causes diseases (Hetem, Rooijakkers, & Ekkelenkamp, 2017, p. 1509). In addition, the application of the bacterium in the agricultural and industrial sector has not been established. The major problem encountered when conducting this experiment is the possible errors, which can play a critical role in shifting the path leading to the wrong identification of the bacterium.

However, the experiment was not repeated due to limited time. Along with that line, the possible sources of error might have emerged from cross-contamination of bacterial strains, wrong observation of the bacteria’s morphology and incorrect identification of the arrangement of the bacterial colony. Also, the culture media used might have been old, staining procedures were not followed as documented, and the slides may have been contaminated prior mounting on the microscope for analysis.


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