Multiple choice

Which of the following tests determines microbial ability to perform mixed-acid fermentation?

  1. Rapid urease test

  2. Indole test

  3. Methyl red test

  4. Voges-Proskauer test

  5. Citrate test
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C Correct answer
Explanation

The methyl red test detects the production of acids formed during metabolism using mixed acid fermentation pathway using pyruvate as a substrate. The pH indicator Methyl Red is added to one tube and a red colour appears at pH's lower than 4.2, indicating a positive test (mixed acid fermentation is used). The solution remaining yellow (pH = 6.2 or above) indicates a negative test, meaning the butanediol fermentation is used.

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