Unknown Bacterium Lab Report
- Slater Robinson
- Nov 29, 2016
- 2 min read

In microbiology lab, I was given a test tube containing an unknown bacterium then told to devise a plan to identify the species that had been given to me and explain how I could relate it to my major. There were five different families and twenty one different species total to choose from. The flow chart with the help of the procedure shows how I reached my final result.
Procedure
The testing for unknown began by conducting the first four initial tests using aseptic technique, those test include: Gram stain (negative rods), 3% KOH (negative), catalase (positive) and oxidase (negative). After reviewing the results, it was evident that the bacterium was in the Enterobacteriaceae family. The negative oxidase and positive catalase confirmed the theory. A TSA plate was then inoculated using the four quadrant method and streaked for isolated colonies. After 24 hours isolated colonies were present, the two phenol red medium tubes were inoculated, both the PR Lactose and PR Arabinose tests both came back positive. This eliminated the possibilities for the bacterium to be anything other than Citrobacter freundii or Escherichia coli. Following these tests, a dihydrogen sulfide production test was done. This test remained yellow indicating it was negative eliminating C. freundii from being a possibility meaning that the bacterium must be E. coli. To confirm this theory, a Voges-Proskauer’s test and a citrate test were completed and both came back negative, still confirming the theory that the bacterium was E. coli. Also, the result of isolated colonies on a TSA plate meant that the bacteria had non-swarming motility, a characteristic not found in E. coli. For the final test, an EMB plate was inoculated and a metallic green sheen covered the medium. Since E. coli was the only organism in this lab to produce such a result, the species of the bacteria was obvious.
In the poultry industry, E. coli is a serious problem that could potentially be lethal when ingested. A biotechnology company called Intralytix focuses on producing and marketing bacteriophage-based products to control bacterial pathogens in environmental, food processing and medical settings. They have already produced several food safety products that target foodborne pathogens including E. coli.
Works Cited
Beecher, C. 2013. New Spray Product Takes Aim at Salmonella on Poultry. Food Safety News. Available at http://www.foodsafetynews.com/2013/03/companys-arsenal-includes-natural-enemy-of-salmonella/#.WD0hs2M-mFI (verified 28 November 2016)
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