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Questions and Answers
What role do cytochromes play in aerobic respiration, according to the principle of the oxidase test?
What role do cytochromes play in aerobic respiration, according to the principle of the oxidase test?
- They act as the final link by transferring electrons to oxygen. (correct)
- They directly produce ATP.
- They initiate the breakdown of glucose.
- They transport carbon dioxide out of the cell.
Why is the oxidase test particularly useful in microbiology?
Why is the oxidase test particularly useful in microbiology?
- To differentiate between Gram-positive and Gram-negative bacteria directly.
- To measure the rate of fermentation in bacteria.
- To identify Enterobacteriaceae (oxidase-negative) from other genera (often oxidase-positive). (correct)
- To determine if an organism is obligately aerobic.
In the oxidase test, what happens to p-phenylenediamine in the presence of cytochrome oxidase and ambient oxygen?
In the oxidase test, what happens to p-phenylenediamine in the presence of cytochrome oxidase and ambient oxygen?
- It remains colorless, indicating a negative result.
- It is reduced, causing the formation of water.
- It is oxidized to indophenol blue, indicating a positive result. (correct)
- It precipitates out of the solution, forming a visible ring.
What is the significance of using artificial electron acceptors like p-phenylenediamine in the oxidase test?
What is the significance of using artificial electron acceptors like p-phenylenediamine in the oxidase test?
What does a negative oxidase test result indicate about an organism's cytochrome system?
What does a negative oxidase test result indicate about an organism's cytochrome system?
Why is the oxidase test important for identifying bacteria with different metabolic capabilities?
Why is the oxidase test important for identifying bacteria with different metabolic capabilities?
How is the tetramethyl derivative of p-phenylenediamine used in the oxidase test procedure?
How is the tetramethyl derivative of p-phenylenediamine used in the oxidase test procedure?
During the oxidase test, if no deep blue color appears within 10 seconds at the site of inoculation, what conclusion can be drawn?
During the oxidase test, if no deep blue color appears within 10 seconds at the site of inoculation, what conclusion can be drawn?
An organism tests positive for the oxidase test. What does this imply about its electron transport chain?
An organism tests positive for the oxidase test. What does this imply about its electron transport chain?
How do facultatively anaerobic species relate to the oxidase test?
How do facultatively anaerobic species relate to the oxidase test?
Flashcards
What is the oxidase test?
What is the oxidase test?
Detects cytochrome oxidase activity in bacteria, aiding in the identification of aerobic or facultatively anaerobic organisms.
What is the role of cytochromes?
What is the role of cytochromes?
Iron-containing hemoproteins act as final link in aerobic respiration, transferring electrons to oxygen, forming water.
What is the oxidase test useful for?
What is the oxidase test useful for?
Useful for identifying Enterobacteriaceae (oxidase-negative) and differentiating from other oxidase-positive genera colonies.
What is the role of p-phenylenediamine dyes?
What is the role of p-phenylenediamine dyes?
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What color is the dye in reduced state?
What color is the dye in reduced state?
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What indicates a positive oxidase test result?
What indicates a positive oxidase test result?
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What material is used in the oxidase test?
What material is used in the oxidase test?
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Describe the oxidase test procedure
Describe the oxidase test procedure
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What indicates a positive oxidase test?
What indicates a positive oxidase test?
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What indicates a negative oxidase test?
What indicates a negative oxidase test?
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Study Notes
- Applies to Gram Negative bacteria.
- Determines if an organism is obligately anaerobic or lacks the enzyme because the cytochrome system is present in facultatively, microaerophilically, and aerobically anaerobic species.
Oxidase Test Principle
- Iron-containing hemoproteins (cytochromes) are the final link in aerobic respiration.
- Cytochromes transfer hydrogen-containing electrons to oxygen, creating water.
- Useful for identifying Enterobacteriaceae (all negative) and colonies suspected of belonging to other genera (positive).
- p-phenylenediamine and dihydrochloride dyes act as artificial electron acceptors in place of oxygen during the cytochrome oxidase test.
- The dye is colourless when reduced.
- p-phenylenediamine oxidizes to indophenol blue with cytochrome oxidase and ambient oxygen present.
Oxidase Test Procedure
- Take a commercial disk containing tetramethyl derivative of p-phenylenediamine and place it on a glass slide.
- Smear a loopful of colony on the disk.
Oxidase Test Interpretation
- Positive result: Deep blue colour at the site of inoculation within 10 seconds.
- Negative result: No deep blue colour within 10 seconds.
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