the reagents were added and the results were recorded early, at 24 hours rather than at the full incubation time at 48 hours, would the color result for the VP (+) bacteria be the same at 24 hours than at 48 hours? If different, explain how the color result is different. What chemical would be missing at 24 hours that is needed for a positive result?
The ingredients in the MR/VP Broth are:
Peptone (protein) 7g
Glucose 5g
Phosphate buffer 5g
Distilled water 1L
Examine the above figure. This figure shows how the pH in the Methyl Red and Voges-Proskauer (MR-VP) broth changes during incubation from time zero to 48 hours with a VP-positive bacteria species.
VP-positive bacteria initially produce lactic acid and temporarily lower the pH, but the lowered pH activates the 2,3-butanediol fermentation pathway. Accumulation of its neutral end products such as acetoin and 2,3-butanediol raises the pH by the end of the incubation time. The acetoin that accumulates in the broth also reacts with the reagents added after incubation to produce a red color.
If the reagents were added and the results were recorded early, at 24 hours rather than at the full incubation time at 48 hours, would the color result for the VP (+) bacteria be the same at 24 hours than at 48 hours? If different, explain how the color result is different. What chemical would be missing at 24 hours that is needed for a positive result?
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