Quiz 3 Unit 3 Bacteria (25 points)
Below is a copy of Quiz 3 (25 points). Read carefully and answer the questions. This is an open book quiz, however, you are expected to do your own work and for the short answer questions write the answers using your own words. Submit your quiz in your Quiz 3 assignment folder as a Word or rtf attachment. To avoid losing extra points don’t forget to start the attachment file name with your last name and initial of your first name; for example the student John Smith would be Smith J.Quiz 3. doc). This is to prevent to prevent problems when I download the quizzes to grade them offline. The quiz is due by 11:59 P.M. Eastern Time, November 15, 2015. See the syllabus for the policy on late submissions.
Part A. Multiple Choice and Fill in the Blank (1 point each)
1. Clostridium tetani and Bacillus cereus are both examples of
a. Gram-negative rods.
b. Normal microflora of the human body.
c. Non-spore forming Gram-positive bacilli.
d. Spore-forming Gram-positive bacilli.
2. Vibrio cholerae is isolated from a GI sample and testing for cholera toxin is negative. Upon coculture with a bacteriophage, testing for cholera toxin becomes positive. This switch from a nontoxic strain to a toxic strain was mediated by:
a. Horizontal gene transfer by conjugation
b. Vertical gene transfer
c. Horizontal gene transfer by transduction
d. Horizontal gene transfer by transformation
3. In a prokaryotic operon, genes that code for enzyme proteins are called
a. structural genes.
b. operator genes.
c. repressor genes.
d. inducer genes.
e. regulatory genes.
4. A plasmid
a. An extrachromosomal piece of DNA that might confer a selective advantage to a microbe.
b. A chromosomal site to which genetic activity can be traced.
c. A molecule that carries the genetic message of the chromosomal DNA.
d. A cytoplasmic structure that transfers an amino acid to mRNA.
5. 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
6. Which of the following is present in Gram-positive bacteria but not in Gram-negative bacteria?
d. Lipoteichoic acid
7. Protein toxins that may interfere with host cell function or damage host cell membranes and are usually secreted by living bacteria are called
a. adhesion factors.
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 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.
8. (3 points) 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? Explain why?
9. (4 points) Name and briefly describe four mechanisms by which antibiotic susceptible bacteria can acquire genes resistant to antibiotics.
10. (3 points) What is an endospore? Describe its structure and function for a bacterial cell. Name at least two infections transmitted to humans by bacterial endospores and the bacteria (genus and species names) that cause them.
11. (3 points) List three different mechanisms by which antibiotics are effective against bacterial infections and give an example of an antibiotic for each of the mechanisms.
12. (3 points) Gram stain investigation: copy your answers to the Gram stain investigation lab.
What were your results? Name the bacteria and appearance after staining.
Describe two ways the food(s) could have become contaminated.
Name two ways contamination could have been avoided.
Did you find any microorganism known not to cause food poisoning? What?
In what ways does Gram staining aide in the identification of unknown bacteria?
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.
13. (2 points) Control slides are missing in The Gram Stain Investigation. What are they and what is their importance in the straining procedure?