MicroBiology Home   Microbiology, 4/e               Prescott, Harley, Klein

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Chapter 6
Review Questions

1. Discuss the reasons why a culture might have a long lag phase after inoculation.

2. Why can’t one always tell when a culture enters the death phase by the use of total cell counts?

3. Calculate the mean growth rate and generation time of a culture that increases from 5 102 to 1 108 cells in 12 hours.

4. If the generation time is 90 minutes and the initial population contains 103 cells, how many bacteria will there be after 8 hours of exponential growth?

5. What does the fact that the YATP of most fermenting bacteria is about 10.5 at high sugar levels mean in terms of the efficiency of biosynthesis and the uses of ATP?

6. Why are continuous culture systems so useful to microbiologists?

7. How do bacterial populations respond in shift-up and shift-down experiments? Account for their behavior in molecular terms.

8. Does the internal pH remain constant despite changes in the external pH? How might this be achieved? Explain how extreme pH values might harm microorganisms.

9. What metabolic and structural adaptations for extreme temperatures have psychrophiles and thermophiles made?

10. Why are generation times in nature usually much longer than in culture?

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