Unknown Lab Report

Topics: Bacteria, Escherichia coli, TSI slant Pages: 4 (1149 words) Published: November 26, 2011
Purpose:

To identify an unknown bacterial specimen using basic laboratory technique and biochemical tests. The unknown bacteria will be one of the following: Enterococcus faecalis, Staphylococcus saprophyticus, Escherichia coli, Enterobacter aerogenes, Proteus vulgaris, Salmonella [I assume typhimurium], or Shigella [either flexneri or sonnei, we used both in our lab during the semester].

Procedure {and observations}:

Observe bacterial colony morphology. {Colonies are large, beige or cream-colored, with irregular borders.} Prepare two slides for gram staining and viewing under a microscope. {Either my gram-stain slides were bad or the microscopes I chose for viewing were not good. No bacteria were found under the microscope.}

Prepare another gram stain of the unknown bacteria. {Gram-positive, coccus shaped bacteria were observed under the microscope. Also noted, the slide may have been inadvertently contaminated during the gram stain process by another person in the laboratory.} [I do think that the gram-stain result is surprising - the two gram-positive cocci species we've been given form medium-sized, round, uniformly colored colonies on TSA plates.

When I say the borders of the bacterial colonies are irregular, I mean that both the shape is irregular and the consistency of the borders is not like the center of the colony. I associate this type of appearance with rod-shaped bacteria in general, whether gram-positive or gram-negative.] Perform catalase test. {Catalase test is positive.}

Inoculate test tubes prepared with the following mediums – Triple Sugar Iron agar slant (TSI slant), Bile Esculin Agar slant (BEA tube), a methyl-red Voges-Proskauer tube (MR-VP tube) and a Urease tube. Incubate the inoculated tubes, to be read at the following lab session. Observe results of tests inoculated during the last session [Note: I used the wrong setting on my digital camera to take these pictures, so they are all blurry! Also, thinking...
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