Esherichia coli

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Several lab experiments were performed to determine the species of an unknown culture. During staining the bacteria was determined to be gram negative after a differential gram stain was performed. The bacteria stained purple. When visualizing the bacteria, the bacteria were rod shaped and largely individuals instead of in groups. It was determined using Thioglycollate agar deep the unknown culture was inoculated using a stabbing technique, and it was determined that the bacteria is facultative.
The bacterium was also inoculated in glucose phenol red fermentation broth and lactose phenol red fermentation broth. Both tubes started red and the turned yellow if acid is present. So when the bacterium ferments it produces an acid and the phenol red turns yellow. There is also a small inverted tube that is placed inside of the tube which indicates whether gas was produced. Both tubes of glucose and lactose turned yellow as well as producing gas bubbles.
The bacterium was also tested to determine whether the bacterium could catabolize the amino acid tryptophan. To determine whether the bacterium can catabolize tryptophan a broth tube was inoculated with the unknown and cultured, and then Kovac’s reagent was added to the tube. The tube with the unknown turned red which is a positive indicator that the unknown is able to catabolize tryptophan. Two more tubes of broth were inoculated and cultured to determine if the unknown organism can ferment glucose through a mixed acid pathway or the butylene glycol pathway. In one tube the methyl-red reagent was added and in the other Barritt’s reagent B was added to the tube and then Barritt’s reagent A was added second. The first test is the methyl-red test and is looking for acid production the fi...

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...e, were better to use to find virulent strains of E coli in Europe than other probes.

Works Cited

Giammanaco, A., Maggio, M., Giammanaco, G., Morelli, R., Minelli, F., Scheutz, F., et al. (1996). Characteristics of Escherichia coli strains belonging to enteropathogenic E. coli serogroups isolated in Italy from children with diarrhea. Journal of Clinical Microbiology, 689-694.
Johnson, J., Murray, A., Kuskowski, M., Schubert, S., Prere, M.-F., Picard, B., et al. (2005). Distribution and Characteristics of Escherichia coli Clonal Group A. Emerging Infectious Dieseases, 141-145.
Microbiology in Pictures. (2013). Retrieved December 03, 2013, from
Silva, R., Toledo, R., & Trabulsi, L. (1980). Biochemical and Cultural Characteristics of Invasive Escherichia coli. Journal of Clinical Microbiology, 441-444.
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