Question

which fermentation pathway is primarily detected by the methyl red test?
lactic acid fermentation
alcohol fermentation
butanediol fermentation
mixed acid fermentation
question 10 (1 point)
what makes up the mr/vp broth?
peptone, glucose and a buffer
only glucose
the bacteria sample
methyl red indicator

Explanation:

• For the first question: The Methyl Red test is used to detect mixed acid fermentation. In mixed acid fermentation, bacteria produce a variety of acids (such as formic, acetic, and lactic acids), which lower the pH of the medium. Methyl red is a pH - sensitive indicator. At a low pH (around 4.4), it turns red. In lactic acid fermentation, mainly lactic acid is produced, but the test is more specific to the mixed acid profile. Alcohol fermentation produces ethanol and \(CO_2\), and butanediol fermentation has a different end - product profile (e.g., 2,3 - butanediol) which is detected by other tests (like the Voges - Proskauer test).
• For the second question: MR/VP broth is composed of peptone (a source of nitrogen and carbon), glucose (a fermentable sugar), and a buffer (usually phosphate buffer). The buffer helps to maintain a relatively stable initial pH. Only glucose would not provide a proper nutrient source for bacterial growth and metabolism studies. The bacteria sample is added to the broth, it is not a component of the broth itself. The methyl red indicator is added separately for the Methyl Red test, not part of the MR/VP broth composition.

Answer:

• First question: Mixed acid fermentation
• Second question: peptone, glucose and a buffer