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24 Cards in this Set
- Front
- Back
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What 3 test does SIM test for?
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Sulfur reduction. indole production from tryptophan. and motility.
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What is the selective and differential media?
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Casein and animal tissue as sources of amino acids (an iron containing compound) and sulfur in the form of sodium thiosulfate.
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SIM media differentiates between what genera?
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Salmonella; francisella; and proteus from the negative Morganella morganii and Providerncia rettgeri.
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What is in the media?
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Casein and animal tissue as sources of amino acids (an iron-containing compound) and sulfur in the form of sodium thiosulfate.
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What is casein and animal tissues and sulfur used for in the medium?
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The source of amino acids. Used to indicate sulfur reduction and a positive test.
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How is sulfur reduction to H2S accomplished by bacteria?
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By the enzyme cysteine desulfurase or thiosulfate reductase.
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How does the enzyme cysteine desulfurase work?
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Catalyzes the putrefaction of the amino acid cystein to pyruvate which produces hydrogen sulfide gas.
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How does the enzyme thiosulfate reductase work?
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Catalyzes the reduction of sulfur (in the form of sulfate) at the end of the anaerobic respiratory electron transport chain. Produces hydrogen sulfide (H2S) gas.
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What happens after H2S production?
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It combines with iron in the form of ferrous ammonium sulfate to form ferric sulfide a black precipitate.
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What does blackening of the medium indicate?
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Sulfur reduction and a positive test.
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What does no blackening of the media indicate?
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No sulfur reduction and a negative reaction.
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What is the substrate enzyme and endproducts?
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Substrate: Amino acids Enzyme: Cystein desulfurase or Thiosulfate reductase. Endproducts: Ferric sulfide
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Indole production?
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Made possible by the presence of tryptophan (contained in casein and animal protein).
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What is the substrate enzyme and endproducts of indole production?
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Substrate: Tryptophan Enzyme: Tryptophanase Endproducts: Pyruvate and ammonia and indole.
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What reagent is added to test for indole?
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Kovacs' reagent.
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What color does the reagent turn if positive and why?
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Red. DMABA reacts with the presence of tryptophanase.
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How is the motility determination made possible by the SIM medium?
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By the reduced agar concentration and the method of inoculation (a single stab from an inoculating needle)
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How does the medium show motility?
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Can be detected by the radiating growth pattern extending outward in all directions from the central stab line in the semi-solid medium.
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What are the applications of the SIM test?
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Used to identify bacteria that are capable of producing indole
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Sulfur reduction results and interpretations?
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Black in the medium-Sulfur reduction (H2S production) No black in the medium-Sulfur is not reduced.
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What is the interpretation of red in the alcohol layer of Kovac's reagent?
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Tryptophan is broken down into indole and pyruvate.
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What is the interpretation of unchanged Kovac's reagent?
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Tryptophan is not broken down into indole and pyruvate.
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What does growth radiating outward from the stab line indicate?
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Motility.
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What is a combination differential media?
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Combinations of ingredients put together in such a way as to allow multiple biochemical determination with a single inoculation.
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