1. Describe the process of bacterial reproduction by binary fission. Explain how it can be said that bacteria are immortal and describe the experiment that suggests bacteria do “age.” Define senescence.
2. Give examples of generation time and be able to calculate population numbers once you have been given a generation time. Be able to determine generation time by looking at a growth curve. Explain why knowing generation time for a particular species and the time of onset of illness can be helpful in determining when the victim became exposed to the pathogen.
3. Describe the bacterial growth curve and tell how it illustrates the dynamics of growth of a population. Compare how what would be going on in the host during phases of the growth curve and what would be happening if the bacteria were growing on lab media. Suppose the bacterial growth curve in Figure 5.4 was produced for a bacterium growing at an optimal temperature of 37o C. Construct a growth curve if the same bacterium was grown at a suboptimal temperature of 23oC.
4. What two genera of bacteria are especially well known for forming endospores? Under what conditions are spores formed and in what part of the growth curve? Contrast vegetative cells with spores. Describe the process of sporulation and the role of dipicolinic acid. Discuss Cano’s claim of germinating bacterial spores that were 25 million years old. Why does the ability to produce spores increase the pathogenicity of an organism? Tell how spores are killed. What is the etiological agent for anthrax? Name one disease caused by spore-forming members of genus Bacillus and three other diseases formed by spore-forming members of genus Clostridium. Tell two reasons why home-canned food that has not been properly cooked before canning provides an ideal environment for toxin-producing Clostridium botulinum. (One of the reasons will be presented in the next section of the chapter.)
5. Explain the difference between optimal temperature for growth of a species and the range of temperatures over which it will grow. Tell the optimal temperatures and ranges for psychrophiles, thermophiles and mesophiles. Tell in which group you would expect to find human pathogens and why. S. aureus and Campylobacter are psychrotropic mesophiles. Explain how this increases their pathogenicity. What is the meaning of “-phile?”
6. Read Textbook Case 5 on pg 148 and answer the three questions asked.
7. Examine Figure 5.8. Do bacteria have the as much tolerance for temperatures above their optimum range as below it?
8. Examine Figure 5.10. Tell why the bacteria are grown in thioglycollate broth and identify the O2 requirement in each tube based on where turbidity is shown. Which of the two spore-forming genera listed above is an obligate aerobe? Name the etiological agent for syphilis and tell its oxygen requirements. The genus Neisseria is responsible for what STD (look in the index) and is capnophilic (which means?)
9. Summarize the pH requirements for bacterial growth. List some commercial uses of acidophiles and name two genera involved. How could acidophilic bacteria impact your health?
10. Tell which methods of preserving food work by overwhelming the ability of bacteria to maintain osmotic homeostasis. Explain why halophiles would or would not likely be human pathogens. Explain why salt-tolerance enhances pathogenicity in species like S. aureus.
11. What is agar and why is it useful for growing bacteria? What percent agar is normally added to broth to convert nutrient broth to nutrient agar? (See Table 5.2.) Contrast complex and synthetic growth media. Contrast selective and differential growth media. Differentiate between growth media and growth medium. What are fastidious bacteria and how do we meet their special needs? What is VBNC? What is “viable?” List two groups of bacteria that have to be grown in tissue cultures.
12. Differentiate between mixed and pure cultures. Why did microbiologists have to learn how to make pure cultures before they could successfully study bacteria as agents of disease? Describe pour-plate and streak-plate methods of isolation. Define turbidity.
13. Review MicroInquiry 5, Identification of Bacterial Species. What does MRSA mean and why do we care? Follow the steps taken to identify MRSA and answer the questions. You will be doing this type of investigation in lab.
.Visit http://microbiology.jbpub.com and
take the quiz that accompanies this chapter. Check out the on-line
MicroFocus stories.