Grossmont Cuyamaca Community College District Microbial Growth Worksheet
BIOLOGY 152; STUDY GUIDE: UNIT 5 MICROBIAL GROWTH
Reading: Chapter 6 Stuff in bold/red you may need to look up on your own (Tortora text) Explain the following terms: Plasmolysis Osmotic pressure halophile reducing media enrichment media generation time capnophile colony colony forming unit (CFU) Answer the following questions:
1. With regard to bacteria, what is meant by the term “growth”?
2. Describe the process of binary fission in bacteria.
3. Why is data for microbial growth generally plotted on a logarithmic scale rather than an arithmetic scale?
4. Draw a graph representing a typical bacterial growth curve, and label and describe each of the four phases of the curve.
5. How do temperature, pH, and osmotic pressure affect microbial growth?
6. Compare and contrast psychrophiles, mesophiles, and thermophiles
7. What is the difference between the minimum growth temperature, maximum growth temperature and optimum growth temperature?
8. What are the four major elements that are required for microbial growth? Briefly describe why each of them is required.
9. Describe the five categories of organisms in terms of oxygen requirements (i.e. obligate aerobe, obligate anaerobe, etc.)
10. What criteria must culture media meet to make them appropriate for growing microorganisms?
11. What material is used to solidify culture media and what is its source?
12. What is the difference between a complex medium and a defined medium?
13. What is the difference between selective media and differential media? Give an example of how each would be used?
14. Given five different organisms with different oxygen requirements, describe the growth you would expect to see in a fluid thioglycolate broth culture of each.
15. How does the catalase test work?
16. Describe two ways of growing anaerobic cultures.
17. Why are rickettsias, chlamydias, and viruses not grown on artificial media?
18. What is a serial dilution? Why would one use a serial dilution?
19. In a serial dilution where 1 ml of culture was plated from the 10-6 dilution, there were 253 colonies on the plate. What is the viable colony count of the organism?
20. What is the difference between a pour plate and a spread plate for quantifying bacteria?
21. Describe how each of the following would be used to measure bacterial growth:
a. Plate counts b. Filtration c. Turbidity using a spectrophotometer d. Direct microscopic count
