Part A. Multiple Choice and Fill in the Blank (1 point each)
1. What was the first clinically effective antibiotic and who discovered it?

2. A plasmid is
a. a molecule that carries the genetic message of the chromosomal DNA.
b. a cytoplasmic structure that transfers an amino acid to mRNA.
c. an extrachromosomal piece of DNA that might confer a selective advantage to a microbe.
d. a chromosomal site to which genetic activity can be traced.

3. Which of the following is an advantage of the human microbiota?
a. It can aid in food digestion.
b. It can inhibit the growth of pathogenic microbes.
c. It can aid in biosynthesis.
d. It can aid in nutrient absorption.
e. All of these

4. Genes A, B, and C are three structural genes of an operon and fall in that order within the operon. A mutation occurs in Gene A that halts transcription early in the gene. What effect will this have on the levels of proteins produced by Genes A, B, and C?
a. Proteins coded by genes A, B, and C will be produced.
b. No proteins coded by genes A, B, and C will be produced.
c. Proteins coded by genes B and C, but not gene A, will be produced
d. Only proteins coded by gene A will be produced.

5. Which of the following conditions leads to maximal expression of the lac operon?
a. lactose present, glucose absent
b. lactose present, glucose present
c. lactose absent, glucose absent
d. lactose absent, glucose present
Part B. Short Answers
Answer the questions below as completely and as thoroughly as possible and where appropriate include a specific example to illustrate. Answer the questions in essay form (not as an outline or bullets) using complete sentences. You may use a diagram or table to supplement your answers, but a diagram or table alone without appropriate discussion will not be adequate for full credit. Reminder: All answers are to be written in your own words and include complete and accurate citations for the sources you used or that support your answer. No points will be earned for answers that do not include complete and accurate citations for the sources of information used to answer the question or that support your answer.
Guidelines on how to cite different types of sources: UMGC (n.d.) APA 6th Edition Citation Examples: General Rules. Retrieved from https://libguides.umgc.edu/apa-examples
For guidelines for how to evaluate the relevance and appropriateness of online sources see
Evaluating Sources of Information topics in Purdue On-line Writing Lab (OWL) Conducting Research (https://owl.english.purdue.edu/owl/section/2/8/ ) and the University of California, Berkeley Library’s Evaluating Resources topics (http://www.lib.berkeley.edu/TeachingLib/Guides/Internet/Evaluate.html

6. (2 points) Is the following statement true or false? Explain why and include an example. Asexually reproducing organisms lack mechanisms for generating genetic diversity within a population.

7. (2 points) Explain how a population of antibiotic-resistant bacteria might develop from non-resistant bacteria and become the dominant strain in response to increased exposure to antibiotics.

8. (3 points) Under conditions of nutrient depletion and other environmental stresses Bacillus anthracis bacteria become dormant remaining viable for many years. When conditions improve (for example when enter a person’s lungs) they cause disease. How do the bacteria survive under adverse conditions? Describe the process and structures of the dormant form. Name the disease caused.

9. (4 points) Antibiotics are selectively toxic. When you take an antibiotic for a bacterial infection, the antibiotic either kills or inhibits the growth of bacterial cells without being toxic for us. Antibiotics are effective by interfering with what four processes? For each, name an antibiotic and the structure on which it acts.

10. (3 points) A-B toxin, superantigens, and membrane-disrupting (pore-forming) toxins are three types of protein exotoxins produced by bacteria. Briefly describe how each of the three types causes disease in the host. Name a specific toxin in each group and the bacterial source (genus and species name) of the toxin, and the disease caused.

Part C. Gram Stain Investigation
Answer the questions using complete sentences.

11. (4 points) Gram stain investigation in Course Module 3
a. What were your results? Name the bacteria and appearance after staining (color and shape) and the food on which each was found.

b. Describe two ways the food(s) could have become contaminated.

c. Name two ways contamination could have been avoided.

d. Did you find any microorganism known not to cause food poisoning? What?

e. In what ways does Gram staining aid in the identification of unknown bacteria?

f. Explain how the differential staining between Gram-positive and Gram-negative bacteria is related to the cell wall structure.

g. What is a mordant and what is its purpose in the Gram stain procedure? What reagent in the Gram stain procedure functions as a mordant?

h. If you forgot to add the iodine, would the Gram-positive bacteria still be purple at the end of the staining procedure? Explain why or why not.

12. (2 points) Control slides are missing in The Gram Stain Investigation. What are they and what is their importance in the straining procedure? Cite sources of information or that support your answer.