Today was a lecture-free day, with 3+ hours of micro lab followed by two more of nutritional pathology case studies. The former was work-intensive and ended with the assignment of "unknown" samples for each student to identify by next week. This, though a little gimmicky, is one of my favorite activities for any lab class because it proves that each of us has actually learned some set of identifying procedures (that we may never be called upon again to physically perform, but still).
TIL: I have a knack for spotting barely something floating in a sea of almost nothing.
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| An array of TSI test results from Wikipedia |
The TSI slant is a very useful test for differentiating between gram-negative bacteria. It uses a diagonally set gel to demonstrate the sugar fermentation, iron oxidation, gas production and aerobic/anaerobic properties of each bacterium. The top, slanted portion is appropriately called the slant while the bottom is the butt. When you are talking to each other about stabbing the butt, context is everything.
If the gel turns yellow it indicates the production of acid through fermentation of one or more sugars. Black indicates the reduction of thiosulfate and production of ferrous sulfide. Bubbles or raising of the agar indicates hydrogen gas production.
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