Question

Suppose that after incubation you examine the jar before opening it and see that the methylene blue strip is blue (or the resazurin strip is pink.) What is the best conclusion about the internal jar environment in such a case?

A. It became aerobic upon being exposed to room temperature.
B. It was anaerobic for most of the incubation period.
C. It was aerobic most of the incubation period.
D. It was aerobic for at least a portion of the incubation period.
E. It was incubated at the wrong temperature.

Answer 1

If the methylene blue strip is blue or the resazurin strip is pink after incubation, the best conclusion is that it was aerobic for at least a portion of the incubation period. The answer is option D.

Step-by-step explanation:

If the methylene blue strip is blue or the resazurin strip is pink after incubation, the best conclusion about the internal jar environment is that it was aerobic for at least a portion of the incubation period.

If the methylene blue strip is blue or the resazurin strip is pink after incubation, it indicates that the internal jar environment was exposed to oxygen at some point during the incubation period. Both indicators serve to detect the presence of oxygen.

The blue color of methylene blue in an anaerobic environment indicates a reducing environment, while the pink color of resazurin in an anaerobic environment indicates oxidation. Therefore, the presence of a blue or pink strip suggests a fluctuation between aerobic and anaerobic conditions during the incubation, revealing variability in the jar's oxygen levels over time.