Microbiology 2420-Lab Practical 2 Questions With Complete Solutions

What does TSI stand for? correct answer: Triple Sugar Iron How do you inoculate a TSI? correct answer: Stab and Drag What does a TSI slant agar select for? correct answer: Differentiates between non-fermenters, glucose fermenters and fermenters of lactose and/or sucrose. It is used to identify intestinal bacteria. What does a black medium on SIM agar indicate? correct answer: Positive for sulfur reduction and H₂S production What agent do you add to the indole test and what organism does it indicate? What is being degraded? correct answer: -Kovack's Reagent -It will create a red ring on the top of liquid indicating E. Coli -The amino acid tryptophan has been degraded into indole What does yellow, black, and red on a TSI slant indicate? correct answer: -Yellow: acid production or fermentation of the sugars in the slant or butt. Gas production is indicated by the agar lifting up or breaking. -Red: negative or uninoculated. -Black: H₂S production due to FeS precipitation (think Salmonella or Proteus). What is Simmon's Citrate agar used for? correct answer: To see if the organism uses citrate as its only carbon source for growth. If the organism on a Simmon's Citrate Agar utilizes citrate it will turn what color? correct answer: It will change from Green to Blue