Question

E. coli and E. aerogenes

Data Shee MRVP Some lab instructions call for a shorter incubation time, while other protocols call for a longer time. Which of the two tests would likely produce more false negatives with a shorter incubation Which test would benefit most from a longer incubation time? What organism does not perform mixed acid fermentation? What organism does not perform 2,3 butanediol fermentation? Name the substrate for the MRVP. Name the products and their pH for the methyl red experiment. Name the products and their pH for the Vogues Proskauer experiment. Is it possible for an organism to be both MR and VP positive? Why is it important to inoculate only a single tube per organism for the MRVP?!

Answer 1

Note: Only the first four questions/parts can be answered at once. Therefore, question (1-4) has been solved with proper explanations.

Answers:

Question 1:

which of the two tests would most likely produce more false negatives with a shorter incubation time?

Answer: The VP test would most likely produce more false negatives with a shorter incubation time because not enough time would have elapsed to produce a detectable amount of acetoin to give a positive result if the incubation time is short.

In The MR test i.e, mixed acid fermentation the pH test would occur without giving false negative as it quickly produces pH change, so it can give correct result in a short incubation period.

Question 2:

which test would likely benefit from a longer incubation time?

Answer:   VP test would likely benefit from a longer incubation time as it would allow the formation of 2,3-butanediol if longer incubation time is given and false-negative test result can be minimized.

Question 3:

What organism does not produce mixed acid fermentation?

Answer: Enterobacter aerogenes would not produce mixed acid fermentation products as it only produces in majority 2,3-butanediol fermentation.

Question 4:

What organism does not produce 2,3-butanediol fermentation?

Answer: Escherichia coli does not produce 2,3-butanediol natively. It can produce ethanol by mixed-acid fermentation.