Vibrio cholerae is isolated from a GI sample and testing for cholera
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
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.
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
b. Vertical gene transfer
c. Horizontal gene transfer by
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. Anextrachromosomal piece of DNA that might confer
a selective advantage to a microbe.
b. Achromosomal site to which genetic activity can
c. Amolecule that carries the genetic message of the
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
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
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?
(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
Name two ways contamination could have
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.
(2 points) Control slides are missing in The Gram Stain Investigation.
What are they and what is their importance in the straining procedure?
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