CHAPTER #6 STUDY GUIDE QUESTIONS
MICROBIAL GROWTH:
Be sure you can answer the following questions before taking Test 2.
OBJECTIVES:
Growth Requirements:
- Identify and differentiate between the two main categories required for microbial growth.
Physical Requirements:
- Classify microbes into five groups on the basis of preferred temperature range.
- Differentiate between the optimum growth temperature and the maximum growth temperature and minimum growth temperature.
- 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.
- 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:
- Briefly describe the roles of carbon (importance and abundance of carbon), hydrogen, oxygen, nitrogen, trace elements and vitamins in microbial growth and reproduction.
- Do all bacterial organisms require oxygen for growth (be sure you understand Table 6.1)? Explain your answer.
- Explain how oxygen can be fatal to organisms by discussing single oxygen, superoxide radical, peroxide anion, and hydroxyl radical.
- Define an organic growth factor, why is it important for microbial growth?
- Explain how biofilms form. Explain why biofilm formation is an important factor in human health.
Culturing Microorganisms:
- 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).
- Capnophiles require what type of environment for culture.
- Compare and contrast the following media: selective, differential, and enrichment. Give an example of each.
Obtaining Pure Cultures:
- Define a colony.
- Describe how pure cultures can be isolated by using the streak plate method.
Growth of Bacterial Populations:
- Define bacterial growth, including binary fission.
- Explain what is meant by the generation time of bacteria.
- Is bacterial growth generally logarithmic or linear – explain your answer.
- Draw and label a bacterial growth curve.
- Describe the four phases of microbial growth and what occurs at each phase of population’s growth.
Direct Measurement of Microbial Growth:
- Briefly explain four direct methods of measuring cell growth (ie plate counts, filtration, MPN method, and direct microscopic count).
- Differentiate between direct and indirect methods of measuring cell growth.