Archive for October 2019

How do some cyanobacteria fix nitrogen while growing aerobically?

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How do some cyanobacteria fix nitrogen while growing aerobically?



a. they don't because nitrogenase is destroyed by oxygen
b. by using special cells called heterocysts that protect the enzyme
c. by using cysts that protect the enzyme
d. they just do it, no special structures or mechanisms
e. they live symbiotically with other organisms that protect the enzyme


Answer: by using special cells called heterocysts that protect the enzyme

Which of the following is true of all biofilms?

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Which of the following is true of all biofilms?



a. They only contain a single species.
b. The EPS may be protein or polysaccharide.
c. Cells in the biofilm are dormant until the bacteria leave the biofilm.
d. The EPS is secreted by the bacteria.
e. It is a continuous monolayer surface deposit.


Answer: The EPS is secreted by the bacteria

You are measuring growth in a bacterial culture. The number of viable cells remains constant, and when you check the medium, you find that the carbon source has been used up. What phase of growth is the culture in?

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You are measuring growth in a bacterial culture. The number of viable cells remains constant, and when you check the medium, you find that the carbon source has been used up. What phase of growth is the culture in?



a. lag phase
b. early log phase
c. late log phase
d. stationary phase
e. death phase


Answer: Stationary phase

In which case would the shortest lag period most likely be observed?

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In which case would the shortest lag period most likely be observed?



a. transfer from complex medium to fresh complex medium
b. transfer from complex medium to minimal medium
c. transfer to a different temperature
d. transfer to a different pH
e. transfer to a different salt concentration


Answer: Transfer from complex medium to fresh complex medium

A cafeteria worker who fails to wash his hands thoroughly and fails to wear gloves inoculates a quiche with 4 E. coli when he uses his finger to test whether it is done. By the time you purchase the quiche, there are 128 E. coli cells in it. How many generations did the cells go through?

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A cafeteria worker who fails to wash his hands thoroughly and fails to wear gloves inoculates a quiche with 4 E. coli when he uses his finger to test whether it is done. By the time you purchase the quiche, there are 128 E. coli cells in it. How many generations did the cells go through?



a. 4
b. 5
c. 8
d. 32
e. 64


Answer: 5

Which of the following statements is false about the E. coli phosphotransferase system (PTS)?

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Which of the following statements is false about the E. coli phosphotransferase system (PTS)?



a. The EnzI complex in the cytoplasm is shared between all PTS transporters.
b. The EnzII complex is specific to the sugar being transported.
c. The phosphate group transferred to the sugar comes from phosphoenolpyruvate.
d. The PTS transport requires energy in the form of ATP.
e. One cannot say that the PTS transports a sugar against its concentration gradient.


Answer: The PTS transport requires energy in the form of ATP.

Which of the following is NOT true about the substrate binding protein (SBP) of the ABC transport system?

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Which of the following is NOT true about the substrate binding protein (SBP) of the ABC transport system?



a. It is found in the periplasm of Gram-negative cells.
b. It is found tethered in Gram-positive cells.
c. It binds to the periplasmic face of the channel and releases the solute.
d. It snags the appropriate solute.
e. It is required for both the uptake and efflux systems.


Answer: It is required for both the uptake and efflux systems.

You have isolated a bacterium from the rumen of a cow and wish to know how it transports glucose into the cell. You perform an experiment that shows uptake of radioactively labeled glucose is equal when the organism is grown in media in the presence and absence of inhibitors of energy production. What is the mechanism of glucose transport in this cell?

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You have isolated a bacterium from the rumen of a cow and wish to know how it transports glucose into the cell. You perform an experiment that shows uptake of radioactively labeled glucose is equal when the organism is grown in media in the presence and absence of inhibitors of energy production. What is the mechanism of glucose transport in this cell?



a. group translocation
b. diffusion
c. facilitated diffusion
d. active transport
e. endocytosis


Answer: Facilitated diffusion

All of the following are true about penicillin EXCEPT

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All of the following are true about penicillin EXCEPT



a. It was discovered by Alexander Fleming.
b. It was an accidental discovery.
c. It is produced by a bacterium.
d. It was the first antibiotic used by humans.
e. It was purified by Florey and Chain.


Answer: produced by a bacterium

You have isolated a bacterium that you believe to be the causative agent of a new disease in frogs. How would you test the third of Koch's postulates?

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You have isolated a bacterium that you believe to be the causative agent of a new disease in frogs. How would you test the third of Koch's postulates?



a. Determine the shape of the bacterial cells.
b. Inject the bacteria into a healthy frog.
c. Isolate the bacterium from a sick frog.
d. Show that the bacterium is NOT present in healthy frogs.
e. Grow a pure culture of the bacterium outside the frog.


Answer: Inject bacteria into a healthy frog

Suppose Pasteur's swan-necked flasks containing boiled broth became cloudy 24 hours after boiling. Which choice could best explain the turbidity or cloudiness in the broth without supporting spontaneous generation?

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Suppose Pasteur's swan-necked flasks containing boiled broth became cloudy 24 hours after boiling. Which choice could best explain the turbidity or cloudiness in the broth without supporting spontaneous generation?



a. Endospores in the broth survived boiling and grew after the broth cooled.
b. Contaminating organisms in the broth killed by boiling became alive again after the broth cooled.
c. Chemicals in the broth came together to form living organisms.
d. The broth allowed light to pass through it with less interference after boiling.
e. Solid material in the broth dissolved during boiling.


Answer: Endospores in the broth survived boiling and grew after the broth cooled.

Legionella is transmitted by

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Legionella is transmitted by



A) airborne transmission.
B) foodborne transmission.
C) person-to-person contact.
D) fomites.
E) vectors


Answer: airborne transmission

A patient has fever, difficulty breathing, chest pains, fluid in the alveoli, and a positive tuberculin skin test. Gram-positive cocci are isolated from the sputum. The patient most likely has

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A patient has fever, difficulty breathing, chest pains, fluid in the alveoli, and a positive tuberculin skin test. Gram-positive cocci are isolated from the sputum. The patient most likely has



A) tuberculosis.
B) influenza.
C) pneumococcal pneumonia.
D) mycoplasmal pneumonia.
E) the common cold


Answer: pneumococcal pneumonia

Which of the following statements regarding tuberculosis is FALSE?

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Which of the following statements regarding tuberculosis is FALSE?



A) Nearly 1/3 of the world's population is infected with tuberculosis.
B) Nearly 1/3 of the world's population shows symptoms of tuberculosis.
C) It is responsible for nearly 2 million deaths per year.
D) At least 1/3 of those who are TB-positive are also HIV-positive.
E) Treatment requires at least six months of antibiotic therapy


Answer: Nearly 1/3 of the world's population shows symptoms of tuberculosis

Which of the following is mismatched?

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Which of the following is mismatched?



A) Burkholderia — melioidosis
B) Coxiella — Q fever
C) Mycoplasma — walking pneumonia
D) Chlamydophila — psittacosis
E) Mycobacterium — whooping cough


Answer: mycobacterium - whopping cough
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