SIM test

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SIM test
2013-04-10 08:00:26

Show Answers:

  1. What is SIM medium used for?
    • Detection of:
    • sulfur reduction
    • Indole production from tryptophan
    • Motility
  2. What are the ingredients in SIM medium?
    • Casein and animal tissue: amino acid
    • Iron containing compound: iindicator
    • Sodium thiosulfate: sulfur
    • Semi solid agar: motility
  3. What are the two enzymes that can reduce sulfur to H2S in bacteria?
    Cysteine desulfurase and thiosulfate reductase
  4. What does cysteine desulfurase do?
    It catalyze the putrefaction of amino acid cysteine to pyruvate and H2S
  5. What does thiolsulfate reductase do?
    Reduction of sulfur in sulfate(end of anaerobic electron transport chain) to SO3 and H2S
  6. What happen when H2S(hydrogen sulfide) reacted with ferrous ammonium sulfate?
    Produce FeS(Ferric sulfide) which is a black precipitate
  7. What color of the medium indicate sulfate reduction?
    blackening of the medium
  8. What does casein and animal protein contain?
  9. What type of enzyme can hydrolyze tryptophan?
  10. What are the products of the hydrolysis of tryptophan?
    • Pyruvate
    • Ammonia(deamination)
    • Indole
  11. What reagent is needed to detect the hydrolysis of tryptophan?
    Kovasc' reagent
  12. What is contain in Kovasc' reagent?
    Dimethylaminobenzaldehy(DMABA) and HCl
  13. What is produce when DMABA reacted with indole?
    A quinoidal(Rosindole dye) that turn the medium red
  14. No red color in the SIM test after Kovasc' reagent is added mean?
    The test is negative. No indole produce so because the tryptophan was not hydrolyze
  15. How do the semisolid medium innoculate to determine motility?
    By a single stab from an inoculating needle
  16. What is the indication for motility?
    Growth that appear to radiate in all direction and appear slightly fuzzy.
  17. What is the SIM test used for?
    • differentiate Enterobacteriaceae species. 
    • Differentiate sulfur-reducing bacteria (Salmonella, Francisella, and Proteus) from non sulfur reducing bacteria (Morganella morganii and Providencia rettgeri)
    • Motility