BioChemistry > EXAM > Biochemical Test - Triple Sugar Iron (TSI) Questions with Answers,100% CORRECT (All)

Biochemical Test - Triple Sugar Iron (TSI) Questions with Answers,100% CORRECT

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Biochemical Test - Triple Sugar Iron (TSI) Questions with Answers Tests for... - CORRECT ANSWER carbohydrate fermentation, gas production, & hydrogen sulfide production TSI slant - CORRECT ANS ... WER contains agar, pH indicator (phenol red), 1% lactose, 1% sucrose, 0.1% glucose, & sodium thiosulfate & ferrous sulfate; as media cools after autoclaving, test tubes placed at slanted angle - provides oxygen-rich surface (aerobic) & oxygen-depleted butt (anaerobic) how the test works - CORRECT ANSWER bacteria that ferment any of the 3 sugars in medium will produce acid byproducts, causing color of red pH-sensitive dye (phenol red) to change to yellow; color changes in butt or butt & slant distinguish which sugars are fermented red slant/yellow but - CORRECT ANSWER glucose-only fermenter yellow slant/yellow butt - CORRECT ANSWER glucose & lactose fermenter, glucose & sucrose fermenter, or glucose & lactose/sucrose fermenter red slant/red butt - CORRECT ANSWER organisms that don't ferment any of the 3 sugars purpose for iron & sulfur compounds - CORRECT ANSWER tests for production of hydrogen sulfide gas hydrogen sulfide (H2S) - CORRECT ANSWER produced if sulfur compound is reduced by bacterial stain; happens when bacterium either degrades AA cysteine during protein degradation or when anaerobic respiration shuttles electrons to sulfur instead of oxygen result from H2S - CORRECT ANSWER when produced, reacts with iron compound to form black precipitate of ferric sulfide; black color is indicator for presence of H2S positive H2S test - CORRECT ANSWER blackening of medium observed in anaerobic butt (bottom) of medium drawback of positive H2S test - CORRECT ANSWER blackening of butt from H2S production may mask acid reaction (yellow) in butt gas production - CORRECT ANSWER under anaerobic conditions (bottom of tube), some bacteria use H+ as an e- acceptor & reduce it to hydrogen has (not very soluble & may accumulate as bubbles or lift agar up); CO2, if produced, may not show as bubbles since it's more soluble in medium [Show More]

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