Exercise # 16 (Mixed Acid Fermentation) Methyl Red Test

Methyl Red (MR) test

test determines whether the microbe performs mixed acids fermentation when supplied glucose

Mixed acid fermentation

one of the two broad patterns, 2-3-butanediol fermentation being another

MR-VP broth

used for both MR Test and VP test. Only the addition of reagent differs, and both tests are carried out consecutively

MR Positive

When the culture medium turns red after addition of methyl red, because of a pH at or below 4.4 from the fermentation of glucose

MR Negative

When the culture medium remains yellow, which occurs when less acid is produced (pH is higher) from the fermentation of glucose