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6. Endospores and persister cells are both used by bacteria to survive harsh conditions. However, these two structures are not similar, and they do not protect against the same harsh conditions.

A. Both endospores and persister cells are in a state of dormancy, but not for the same reasons. Explain the difference between persister dormancy and endospore dormancy. What is involved in each, and how does the level of inactivity compare?

B. Endospores are resistant to heat damage. Explain why. Would you predict that persisters are also resistant to heat damage?

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Sixta Kovacek
Sixta KovacekLv2
28 Sep 2019

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Class 6: Viruses (and Cells, continued)


Making connections: viruses and microbes Match the cell biology concept (on page 1) with an important application of that concept (on page 2). Then answer the follow-up questions at the bottom of page 2.


Cell Biology concepts
1. Bacteria that cannot construct new cell wall material become fragile and break down.
2. During influenza infection, the viral enzyme neuraminidase is required to release new viruses from the host cell in which they were made. Once released, the new viruses can infect many additional cells.
3. Thermus aquaticus is a bacterium found in hot springs and can live at temperatures up to ~80°C (175°F). It has adapted so that its enzymes are most functional at the elevated temperatures, compared with many organisms’ enzymes that function best ~37°C (98°F).
4. Until the isolation and investigation of retroviruses, scientists thought that RNA could be copied from DNA, but DNA could not be copied from RNA. Research on this class of viruses led to an update to this “Central Dogma” of biology.
5. Some bacteria have adapted, so that the enzymes involved in making cell wall materials have a slightly different shape and can no longer be bound by certain drugs.
6. Rhizobia are bacteria that colonize the roots of certain plants (legumes, including beans and peas). The host plant benefits from the prokaryotes’ ability to “fix” nitrogen, converting N2 from the atmosphere into a form that is usable by the plant.
7. Many species of bacteria contain the enzyme cellulase. More than 10 billion such bacteria and other symbiotic microbes may be found in a single milliliter of material from inside the digestive system of ruminant mammals.
8. Fungi, including those that cause athlete’s foot, use ergosterol to maintain healthy membranes. Animal cells do not make ergosterol, they use a similar lipid – cholesterol.
9. During retrovirus infection, a DNA copy is made of the virus’s RNA genome. A cut is made in the host cell’s DNA and the DNA copy of the viral genome is pasted into the host chromosome by a viral enzyme called integrase.
10. Prokaryotic cells contain smaller ribosomes (“70S” ribosomes) than eukaryotic cells (“80S” ribosomes). Both types of ribosomes synthesize proteins, but the macromolecules they use to do it are somewhat different.



2
Applications
_______ Oseltamivir, also called Tamiflu, binds and inhibits the viral protein neuraminidase.
_______ Clotrimazole is a drug that is used to treat certain infections. It interferes with synthesis of ergosterol, a lipid involved in phospholipid membranes.
_______ Penicillin is a drug that interferes with synthesis of peptidoglycans (these are biological molecules that are part protein and part carbohydrate) that are present in certain cell walls.
_______ HIV is often treated with several drugs that inhibit different parts of the viral replicative cycle. Raltegravir is an example of a drug that interferes with the integration of viral genes into the host cell’s chromosome.
_______ Cows, like other vertebrates, lack the ability to breakdown cellulose. Yet they are able to live on a diet of grass and other vegetation high in cellulose.
_______ Enzymes isolated from extremophiles have been very useful in laboratory research. For example, Taq polymerase facilitates PCR, a revolutionary technique for production of DNAs of particular sequences, which requires cycling reactions through high temperatures.
_______ Plants and animals require nitrogen to make biological macromolecules, however they’re unable to convert atmospheric nitrogen (N2) into a biologically useful form.
_______ Azithromycin is a drug that binds to 70S ribosomes and blocks synthesis of any new proteins.
_______ Methicillin-Resistant Staphylococcus aureus (MRSA) can cause life-threatening infections of the skin and bloodstream. One of the reasons MRSA infections are so serious is that they are resistant to treatment by many antibiotics, including methicillin and penicillin.
_______ The enzyme reverse transcriptase, isolated from retroviruses, is an important tool in molecular biology research. Scientists interested in learning what genes are turned on in particular cells use it to make DNA copies of RNAs they are studying (The DNA copies are useful because they are more stable).


When you have completed the matching activity, answer these follow-up questions:
• What types of infections can be treated with the following drugs?
o Penicillin
o Clotrimazole
o Azithromycin
o Tamiflu
o Raltegravir
• Why are these drugs (above) safe for you to take? That is, why don’t they kill your cells?
• Cancer cells are your own human cells that have become deregulated so that they divide and pile up in an uncontrolled way. Many chemotherapy drugs treat cancer by interfering with cell division and other cell processes.
o Why are there so many more side effects for individuals undergoing chemotherapy than for individuals taking antibiotics?

Highlight or bold the answer you select for multiple choice or type in your answer in the blank space provided.

1. Which of the following is not true of the nervous system?

Consists of central and peripheral systems

(b) Central nervous system is composed of brain and spinal cord

(c) Ganglia are part of brain

(d) Meninges are membranes that cover brain and spinal cord

(e) Normally free of microbes

2. Which of the following is a common cause of meningitis in nonimmunized young children?

(a) Streptococcus pneumoniae

(b) Escherichia coli

(c) Staphylococcus

(d) Haemophilus influenzae

(e) None of the above

3. A complication of infection with this organism (Waterhouse-Friderichsen syndrome) can occur if the organism becomes widely distributed in the body, leading to endotoxin shock and death. The organism is:

(a) Haemophilus influenzae type A

(b) Neisseria meningitidis

(c) Haemophilus influenzae type B

(d) Streptococcus pneumoniae

(e) Listeria monocytogenes

4. Which of the following bacterial meningitis diseases currently is the most common type in the U.S., with increased incidences in infants and in the 15- to 24-year-old age group, and has three types or strains of the infectious microbe?

(a) Haemophilus meningitis

(b) Listeriosis

(c) Streptococcus meningitis

(d) Meningococcal meningitis

(e) a and c

5. Before development of a vaccine against this microbe, the disease it caused accounted for two-thirds of bacterial meningitis cases during the first year of life but is still the number one leading cause of mental retardation in patients who survive serious disease due to permanent central nervous system disorders. What is the microorganism?

(a) Haemophilus influenzae type B

(b) Haemophilus influenzae type A

(c) Neisseria meningitidis

(d) Streptococcus pneumoniae

(e) Listeria monocytogenes

6. Which of the following bacteria that may cause meningitis is Gram-positive and therefore does not cause endotoxin shock in infected individuals?

(a) Escherichia coli

(b) Neisseria meningitidis

(c) Listeria monocytogenes

(d) Haemophilus influenzae type B

(e) None of these

7. Avid swimmers and hot tub enthusiasts sometimes acquire an opportunistic infection caused by Naegleria fowleri that results in a meningoencephalitis. This organism is a (an):

(a) Protist

(b) Helminth

(c) Bacteria

(d) Amoeba

(e) a and d

8. Which of the following in NOT true about listeriosis?

(a) Foodborne transmission is the most common source of infection.

(b) It is a leading cause of bacterial meningitis today.

(c) It is responsible for many cases of fetal damage and death.

(d) It is sometimes acquired as a zoonosis.

(e) Individuals with impaired immune systems are highly susceptible to this disease.

9. Viral meningitis is usually always fatal if untreated, unlike bacterial meningitis, which is always self-limiting and nonfatal. True or false?

10. Which of the following is acid-fast and causes Hansen's disease?

(a) Mycobacterium tuberculosis

(b) Clostridium tetani

(c) Neisseria meningitidis

(d) Haemophilus influenzae

(e) Mycobacterium leprae

11. An immunofluorescent antibody test (IFAT) has replaced the older test for the presence of inclusions in neurons (Negri bodies) for the detection of infections caused by:

(a) Neisseria meningitidis

(b) Enteroviruses

(c) Mumps virus

(d) Rabies virus

(e) Haemophilus influenza

12. The viruses that cause encephalitis are most likely to be:

(a) Togaviruses

(b) Enteroviruses

(c) Mumps virus

(d) Rabies virus

(e) Hepatitis viruses

13. What do the following viral encephalitis diseases have in common: eastern equine encephalitis, western equine encephalitis, Venezuelan equine encephalitis, St. Louis encephalitis, West Nile fever?

(a) They are all caused by the same virus.

(b) They are have the horse as a common intermediate host.

(c) They are all transmitted into the body through the bite of an infected mosquito.

(d) Birds are never involved in the life cycle of the viruses that cause these diseases.

(e) Both a and d.

14. The only bacterium known to damage peripheral nerves is:

(a) Naegleria fowleri

(b) Mycobacterium leprae

(c) Streptococcus pneumoniae

(d) Neisseria meningitidis

(e) Haemophilus influenzae

15. All of the following are true about Clostridium tetani, the causative agent of tetanus, EXCEPT:

(a) They are spore-forming rods.

(b) They are part of the normal bowel microflora of horses, cattle, and humans.

(c) They produce a powerful exotoxin that mediates the disease.

(d) Their toxin elicits muscle stiffness, spasms, and paralysis in the victim.

(e) They require oxygen to survive.

16. A vaccine that was developed in 1933 has proven effective in reducing the incidence of disease caused by:

(a) Clostridium botulinum

(b) Mycobacterium leprae

(c) Clostridium tetani

(d) Streptococcus pneumoniae

(e) Listeria monocytogenes

17. The most common form of disease caused by Clostridium botulinum is:

(a) Infant

(b) Wound

(c) Lung, following exposure to aerosols

(d) Foodborne

(e) None of these

18. The endospores of this organism are the most heat-resistant known; it is:

(a) Clostridium tetani

(b) Clostridium botulinum

(c) Mycobacterium leprae

(d) Streptococcus thermicos

(e) Listeria monocytogenes

19. All of the following are true about Clostridium botulinum, the causative agent of botulism, EXCEPT:

(a) Their ability to form toxin depends on infection with a bacteriophage.

(b) They can produce one of eight different toxins, all of which cause human disease.

(c) They produce the most potent toxin known.

(d) Although their endospores are highly heat-resistant, their toxin can be inactivated by only a few minutes' boiling.

(e) All of the above are true.

20. All of the following are true about poliomyelitis EXCEPT:

(a) Most poliovirus infections are inapparent or mild and nonparalytic.

(b) Polio can be caused by three strains of picornaviruses.

(c) The Salk vaccine contains live, attenuated polioviruses while the Sabin vaccine contains formalin-inactivated polioviruses.

(d) Transmission is by the fecal-oral route and pharyngeal secretions.

(e) Poliomyelitis has afflicted man for thousands of years.

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