Discussion:
Microbiology Study Questions
1. Clostridium and Streptococcus are both catalase-negative. Streptococcus grows by fermentation. Why is Clostridium killed by oxygen, whereas Streptococcus is not?
2. Assume that after washing your hands, you leave ten bacteria cells on a new bar of soap. You then decide to do a plate count of the soap after it was left in the soap dish for 24 hours. You dilute 1g of the soap 1:106 and plate it on standard plate count agar. After 24 hours of incubation, there are 168 colonies. How many bacteria were on the soap? How did they get there?
3. Why is each of the following bacteria often resistant to disinfectants?
- 1. Mycobacterium
- 2. Pseudomonas
- 3. Bacillus
4. Explain why gram-negative bacteria are more resistant to biocides than gram-positive bacteria. Be specific and descriptive in your response. A description of the differences between gram-negative and gram-positive bacteria should be included, along with an explanation of why any of those differences would have anything to do with the actions of biocides.
5. Ciprofloxacin, erythromycin, and acyclovir are used to treat microbial infections. Ciprofloxacin inhibits DNA gyrase. Erythromycin binds in front of the A site on the 50S subunit of a ribosome. Acyclovir is a guanine analog.
- 1. What steps in protein synthesis are inhibited by each drug?
- 2. Which drug is more effective against bacteria? Why?
- 3. Which drug is more effective against viruses? Why?
- 4. Which drugs will have effects on the host's cells? Why?
- 5. Use the index to identify the disease for which acyclovir is used. Why is it more effective than erythromycin for treating this disease?
- 6. Design an experiment using the vaccinia virus to make a vaccine against AIDS virus (HIV)