Questions and Answers
What type of medium is the Triple-Sugar Iron Agar (TSIA)?
Differential medium.
The Triple-Sugar Iron Agar medium tests for what?
An organism's ability to ferment selected carbohydrates and to produce hydrogen sulfide (H2S).
What does the TSIA medium contain?
3 sugars, a pH indicator (phenol red), two sources of sulfur (cysteine & thiosulfate), an iron salt, and a general nutrient base (peptone, yeast extract).
Match the sugars in TSIA to their concentrations:
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What color is phenol red at neutral pH values?
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What color is phenol red under acidic conditions?
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What color is phenol red under alkaline conditions?
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What are the two sources of sulfur in a TSIA medium?
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What is the role of iron salt in the TSIA medium?
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Color reactions in the medium allow you to differentiate between what?
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It is possible to determine if the organism uses sucrose or lactose, but not which of these sugars specifically.
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How is the TSIA medium inoculated?
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How long should TSIA slants be incubated?
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What are the components of TSIA results?
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If an organism can metabolize glucose and another sugar, what will be the color of the slant and butt?
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In TSIA, an acid reaction is when?
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If the organism can use only glucose, what will be the color of the butt and slant?
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What do organisms that do not use any of the sugars in the medium do?
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Protein catabolism and deamination of amino acids release what?
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Some organisms utilize sulfur compounds as what?
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Hydrogen sulfide is associated with what smell?
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Hydrogen sulfide gas is invisible.
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What functions to detect the production of hydrogen sulfide in the TSIA medium?
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The iron salt reacts with hydrogen sulfide to produce what?
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The result of iron salt plus hydrogen sulfide is what?
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Iron sulfide is visible as what in the medium?
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If the black precipitate is present, then the organism is classified as what?
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What do the results K, A, and G indicate in TSIA interpretation?
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Interpret the results of (K/A) or (Red/Yellow).
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If TSIA results are Red/Yellow, then the abbreviation will be?
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What does K/A, G indicate in TSIA results?
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What is indicated from results showing an acid butt and alkaline slant?
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What do TSIA results include?
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What are the materials needed for the TSIA procedure?
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Study Notes
TSIA Overview
- Triple-Sugar Iron Agar (TSIA) is a differential medium used in microbiology.
- It assesses an organism's ability to ferment selected carbohydrates and produce hydrogen sulfide (H2S).
Composition of TSIA
- Contains 3 sugars: 0.1% Glucose, 1% Sucrose, and 1% Lactose.
- Includes a pH indicator (phenol red) to visualize pH changes.
- Has two sulfur sources: cysteine (a sulfur-containing amino acid) and thiosulfate (S2O32-).
- Incorporates an iron salt and a general nutrient base (peptone, yeast extract).
pH Indicator Reactions
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Phenol red colors:
- Red at neutral pH.
- Yellow under acidic conditions.
- Bright red under alkaline conditions.
Function of Iron Salt
- Iron salt is critical for detecting hydrogen sulfide production.
- Reacts with hydrogen sulfide to form iron sulfide, which appears as a black precipitate in the medium.
Interpretation of Results
- Results assess the color reaction of the slant and butt, and the production of hydrogen sulfide and gas.
- Common result interpretations:
- (A/A): Both slant and butt turn yellow from acid reactions indicating that both glucose and another sugar are fermented.
- (K/A): The slant remains red (alkaline) and the butt turns yellow (acid), showing that only glucose was fermented.
- (K/K): Both slant and butt remain alkaline indicating protein catabolism.
Gas Production
- Bubbles in the medium can be indicated by the notation G, showing gas production during fermentation.
Additional Notes
- Prolonged incubation beyond 24 hours can lead to reversion, yielding inconclusive results.
- If an organism does not utilize any of the sugars, it may catabolize proteins, producing ammonia, resulting in a bright red appearance (alkaline).
- Hydrogen sulfide is associated with the rotten egg smell and is invisible in its gas form.
Practical Procedure
- TSIA inoculation involves stabbing the butt and streaking the surface of the slant with an inoculating needle, followed by incubation.
Summary of Common Results
- Acid Butt and Alkaline Slant (K/A): Only glucose was fermented.
- Acid Butt and Acid Slant (A/A): Both glucose plus another sugar (lactose or sucrose) were fermented.
- Black Precipitate: Indicates hydrogen sulfide production, confirming organism classification as H2S positive.
Required Materials
- Inoculating loop, inoculating needle, and 4 tubes of Triple-Sugar Iron Agar for the TSIA procedure.
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Description
Explore the essential concepts of the Triple-Sugar Iron Agar (TSIA) in this set of flashcards. Learn about its differential medium nature, carbohydrate fermentation capabilities, and sulfur sources. Perfect for microbiology students looking to reinforce their understanding of this critical lab component.
