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What is SIM medium used for?
- Detection of:
- sulfur reduction
- Indole production from tryptophan
What are the ingredients in SIM medium?
- Casein and animal tissue: amino acid
- Iron containing compound: iindicator
- Sodium thiosulfate: sulfur
- Semi solid agar: motility
What are the two enzymes that can reduce sulfur to H2S in bacteria?
Cysteine desulfurase and thiosulfate reductase
What does cysteine desulfurase do?
It catalyze the putrefaction of amino acid cysteine to pyruvate and H2S
What does thiolsulfate reductase do?
Reduction of sulfur in sulfate(end of anaerobic electron transport chain) to SO3 and H2S
What happen when H2S(hydrogen sulfide) reacted with ferrous ammonium sulfate?
Produce FeS(Ferric sulfide) which is a black precipitate
What color of the medium indicate sulfate reduction?
blackening of the medium
What does casein and animal protein contain?
What type of enzyme can hydrolyze tryptophan?
What are the products of the hydrolysis of tryptophan?
What reagent is needed to detect the hydrolysis of tryptophan?
What is contain in Kovasc' reagent?
Dimethylaminobenzaldehy(DMABA) and HCl
What is produce when DMABA reacted with indole?
A quinoidal(Rosindole dye) that turn the medium red
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
How do the semisolid medium innoculate to determine motility?
By a single stab from an inoculating needle
What is the indication for motility?
Growth that appear to radiate in all direction and appear slightly fuzzy.
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)
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