CHAPTER #6 STUDY GUIDE QUESTIONS
MICROBIAL GROWTH:
Be sure you can answer the following questions before taking Test 2.
OBJECTIVES:
Growth Requirements:
1. Identify and differentiate between the two main categories required for microbial growth.
Physical Requirements:
2. Classify microbes into five groups on the basis of preferred temperature range.
3. Differentiate between the optimum growth temperature and the maximum growth temperature and
minimum growth temperature.
4. Identify the desired pH values for most bacterial cells (why is this important to humans). Why it
important to control the pH of culture media when growing microbes - explain.
5. Explain the importance of osmotic pressure to microbial growth, note be sure you understand
what osmosis is. Differentiate between extreme halophiles, obligate halophiles, and facultative
halophiles.
Chemical Requirements:
6. Briefly describe the roles of carbon (importance and abundance of carbon), hydrogen, oxygen,
nitrogen, trace elements and vitamins in microbial growth and reproduction.
7. Do all bacterial organisms require oxygen for growth (be sure you understand Table 6.1)? Explain
your answer.
8. Explain how oxygen can be fatal to organisms by discussing single oxygen, superoxide radical,
peroxide anion, and hydroxyl radical.
9. Define an organic growth factor, why is it important for microbial growth?
10. Explain how biofilms form. Explain why biofilm formation is an important factor in human health.
Culturing Microorganisms:
11. Distinguish between chemically defined and complex media (note, this information should be
familiar as much of it was discussed in Lab 3 or 4 depending on which class you are registered for
– hybrid or on campus).
12. Capnophiles require what type of environment for culture.
13. Compare and contrast the following media: selective, differential, and enrichment. Give an
example of each.
Obtaining Pure Cultures:
14. Define a colony.
15. Describe how pure cultures can be isolated by using the streak plate method.
Growth of Bacterial Populations:
16. Define bacterial growth, including binary fission.
17. Explain what is meant by the generation time of bacteria.
18. Is bacterial growth generally logarithmic or linear – explain your answer.
19. Draw and label a bacterial growth curve.
20. Describe the four phases of microbial growth and what occurs at each phase of population’s
growth.
Direct Measurement of Microbial Growth:
21. Briefly explain four direct methods of measuring cell growth (ie plate counts, filtration, MPN
method, and direct microscopic count).
22. Differentiate between direct and indirect methods of measuring cell growth.