Download Reading Guide for Week 8

Reading Guide for Week 8 – Bio260
Colleen Sheridan
Stage 03 – Treatment and Resistance
Our bacteria have established themselves in our host’s body, are using our body as a source of nutrients in the
proper environment, and are growing out of our control. So we head to the doctor for help. In this unit, we’ll
learn about how antimicrobials work to fight off pathogens, and we’ll learn about the devastating consequences
of their overuse.
In this week’s reading you will learn about:
1. The mechanisms that bacteria use to cause resistance to a drug
2. How antibiotic resistance can happen: bacterial genetics
Essential question: As you are reading, keep asking yourself, “How is this helping me to understand how
antimicrobial resistance can happen?”
Chapter 20: Antimicrobial Medications (section 20.5)
1. How do organisms develop resistance to antibiotics? Look at Figure 20.13 and answer the following
questions:
A) How does the population growth of bacteria change over time? Draw a graph with time on
the x-axis and number of bacteria on the y-axis. The initial timepoint on our x-axis (let’s call this Time
0) is our population of bacteria before the drug is given (top of Figure 20.13), the next timepoint (Time
1) is our population of bacteria after initial exposure to the antimicrobial drug (middle of Figure 20.13),
and the last timepoint (Time 2) is our population of bacteria sometime later, but still in the presence of
the antimicrobial drug (bottom of Figure 20.13).
B) Now let’s describe the variation of this population of bacteria in Figure 20.13: Before the
antimicrobial drug is given (top of Figure 20.13), are there any resistant strains already present in the
population? How do you think they came about? Make your initial hypotheses here, then keep reading
in this section to learn more.
C) Would you say that the resistant bacteria were pre-existing (already present) in the population
before exposure to the drug, or did the drug cause that one bacterium to change from being sensitive to
being resistant to the drug?
D) You can see in Figure 20.13 that the resistant bacteria are being selected for by the drug in
their environment. Would you say this is a random (happens by chance) selection or a nonrandom
(happens by a very specific mechanism) selection? Why?
E) What evidence from this Figure could you use to support this statement, “The bacterial
population adapted to the drug” (Hint: How does the population at the bottom of Figure 20.13 differ
from the population at the top? What drug environment is the population at the top in, compared to the
population at the bottom?)
F) Does inheritance of genetic information play a role in the development of drug resistance?
How?
G) To sum this figure up, write a paragraph that explains how drug resistance happens using the
following key terms: population, pre-exisiting variation, selection, inheritance, adaptation
2. What are some mechanisms that bacteria have evolved for resistance? Be able to explain Figure 20.14
3. How can bacteria acquire resistance? We’ll tackle this question more deeply in Chapter 8.
4. What are examples of emerging resistance seen in Enterococci, Staphylococcus aureus, Streptococcus
pneumoniae, Mycobacterium tuberculosis, and Enterobacteriaceae?
5. How can we slow the emergence and spread of antimicrobial resistance?
Chapter 8: Bacterial Genetics (skip 8.5)
1. What is meant by the terms genotype and phenotype?
2. What contribution was made by Barbara McClintock?
3. What is meant by vertical gene transfer? By horizontal gene transfer?
4. What is an auxotroph? A prototroph? A wild type strain? How would you indicate a streptomycin resistant
strain using the three-letter abbreviation convention?
5. What is a spontaneous mutation? Know the definition of a base pair mutation and frameshift mutation.
6. Understand the following types of base pair mutations: silent mutation, missense mutation, and nonsense
mutation.
7. What are transposons and how can they contribute to mutations?
8. What is an induced mutation? What are examples of chemical mutagens? Know how they induce changes in
the DNA or contribute to the formation of mutations.
9. How do UV radiation and x-rays contribute to mutations?
10. What are the different mechanisms that bacteria can use to repair their damaged DNA?
11. What are the three ways to transfer genetic material?
12. Explain the importance of a “replicon” to the inheritance of genetic material (passing on genes to daughter
cells).
13. Define: donor cell, recipient cell, homologous recombination, competent cell, F+ and
F- cells.
14. What do transformation, conjugation, and transduction have in common? What is different?
15. What do you need to have transformation occur? What about conjugation? What about transduction?
16. Explain the two types of transduction. How are they different? How are they similar?
17. What type of virus is necessary for generalized transduction? For specialized transduction?
18. Understand conjugation between the following cells: F+ and F-.
19. What is the definition of the following terms: F(+), F’, Hfr, and F(-). Which are able to participate in
conjugation?
20. What is meant by the term mobilome?
21. What are plasmids?
22. What are R plasmids? What genes are found on plasmids that allow them to be transferred to other
organisms?
23. On transposons, what is an insertion sequence? What is a composite transposon?