Chapter 7
Microbial Physiology and Genetics
Learning Objectives
Chapter 7 introduces students to aspects of microbial physiology, such as enzymes, metabolism
(catabolic and anabolic reactions), oxidation–reduction reactions, biochemical pathways, aerobic
respiration, and fermentation. Microbial genetic topics discussed in Chapter 7 include mutations,
the various ways in which bacteria acquire new genetic information (lysogenic conversion,
transduction, transformation, and conjugation), genetic engineering, and gene therapy. The
information in Chapter 7 is considered essential in an introductory microbiology course.
Possible Student Laboratory Activities
1. Instructors could show videotapes or DVDs pertaining to any of these topics: microbial
physiology, microbial genetics, genetic engineering, gene therapy. Possible online sources
include Films for the Humanities & Sciences (www.films.com), Insight Media (www.insightmedia.com), Carolina (www.carolina.com), and Ward’s (www.wardsci.com).
2. Check for applicable laboratory activity kits at the Carolina and Ward’s Web sites.
3. Check Edvotek (www.edvotek.com) for applicable laboratory activities.
4. Appropriate laboratory exercises are described in the various microbiology laboratory manuals
available from Amazon (www.amazon.com).
Answers to the Critical Thinking Questions
1.
Give two possible explanations why an obligate anaerobe is unable to live in the presence
of oxygen?
Answer: The particular anaerobe may lack either superoxide dismutase or catalase. Without
superoxide dismutase, the organism would be unable to neutralize the harmful effects of
superoxide anions. Without catalase, the organism would be unable to neutralize the
harmful effects of hydrogen peroxide.
2.
Assume that you are a microbiologist who has been doing research on a penicillinsensitive strain of Staphylococcus aureus for many months. One day you discover that
the organism is now resistant to penicillin. You know that it has not come in contact with
any other species of bacteria, nor has it come in contact with the DNA from any other
species of bacteria. What are the two possible explanations for its sudden change from
penicillin susceptibility to penicillin resistance?
Answer: (1) One possibility is that a chromosomal mutation occurred that altered a penicillin-
binding site, so that penicillin is no longer able to bind to it. (2) Another possibility is that
a chromosomal mutation occurred that altered the organism’s membrane permeability, so
that penicillin is no longer able to enter the cell.
3.
Several products were mentioned in this chapter, which are being produced by
genetically engineered bacteria and yeasts. Using the Internet, can you find others?
Answer: Requires an individual response. A good place to start is
http://en.wikipedia.org/wiki/Genetic_engineering.
4.
Use the Internet to learn why some people are against genetically modified food.
Answer: Requires an individual response. A good place to start is
http://library.thinkquest.org/TQ0312650/food.htm.
5.
Be prepared to discuss these processes: lysogenic conversion, transduction,
transformation, and conjugation.
Answer: All are described in Chapter 7.
6.
Using the Internet, prepare a brief written report on the current status of gene therapy in
medicine.
Answer: Requires an individual response. A good place to start is
http://en.wikipedia.org/wiki/Gene_therapy.