Question 1

Organisms that are indifferent to the presence of oxygen and do not use it are

Accepted Answer

A) aerotolerant anaerobes. 
B) facultative anaerobes. 
C) obligate aerobes. 
D) microaerophiles. 
A) aerotolerant anaerobes. 
B) facultative anaerobes. 
C) obligate aerobes. 
D) microaerophiles.

Question 2

Organisms that require gaseous oxygen for metabolism are referred to as

Accepted Answer

A) facultative aerobes. 
B) obligate aerobes. 
C) facultative anaerobes. 
D) microaerophiles. 
A) facultative aerobes. 
B) obligate aerobes. 
C) facultative anaerobes. 
D) microaerophiles.

Question 3

A pure culture in exponential growth phase has a bacterial concentration of 6.4 x 108 cells/ml. If the bacterium has a generation time of 1 h, how long ago was the cell concentration 8.0 x 107 cells/ml?

Accepted Answer

A) 1 h 
B) 2 h 
C) 3 h 
D) 4 h 
A) 1 h 
B) 2 h 
C) 3 h 
D) 4 h

Question 4

The optimum pH for growth of most species of bacteria is

Accepted Answer

A) pH 5. 
B) pH 7. 
C) pH 9. 
D) pH 6. 
A) pH 5. 
B) pH 7. 
C) pH 9. 
D) pH 6.

Question 5

Agar replaced gelatin as the gelling (solidifying) agent for media because

Accepted Answer

A) agar is much cheaper. 
B) much fewer bacteria can break down agar than gelatin. 
C) agar is solid at body temperature. 
D) gelatin became unavailable during World War II. 
E) much fewer bacteria can break down agar than gelatin AND agar is solid at body temperature. 
A) agar is much cheaper. 
B) much fewer bacteria can break down agar than gelatin. 
C) agar is solid at body temperature. 
D) gelatin became unavailable during World War II. 
E) much fewer bacteria can break down agar than gelatin AND agar is solid at body temperature.

Question 6

High concentrations of salt and sugar in foods

Accepted Answer

A) are useful in preserving the food. 
B) tend to draw water out of a cell. 
C) tend to force water into a cell, causing plasmolysis. 
D) have no effect on water availability. 
E) are useful in preserving the food AND tend to draw water out of a cell. 
A) are useful in preserving the food. 
B) tend to draw water out of a cell. 
C) tend to force water into a cell, causing plasmolysis. 
D) have no effect on water availability. 
E) are useful in preserving the food AND tend to draw water out of a cell.

Question 7

A hot tub (approx. 104 deg. F or 40 deg. C) would most likely contain

Accepted Answer

A) psychrophiles. 
B) partiers. 
C) thermophiles. 
D) mesophiles. 
A) psychrophiles. 
B) partiers. 
C) thermophiles. 
D) mesophiles.

Question 8

The solidifying agent used most successfully in bacterial nutrient media is

Accepted Answer

A) gelatin. 
B) peptone. 
C) agar. 
D) starch. 
A) gelatin. 
B) peptone. 
C) agar. 
D) starch.

Question 9

During which phase of the bacterial growth curve does the total number of viable cells decline?

Accepted Answer

A) stationary 
B) lag 
C) exponential 
D) death 
A) stationary 
B) lag 
C) exponential 
D) death

Question 10

A urine sample with more than 100,000 organisms is considered indicative of infection. A urine sample containing 5,000 bacteria, with a generation time of 30 minutes, sits for 3 hours before finally being assayed. How many bacteria will then be present within the sample?

Accepted Answer

A) 10,000 
B) 64,000 
C) 100,000 
D) 320,000 
A) 10,000 
B) 64,000 
C) 100,000 
D) 320,000

Question 11

One would expect most strict anaerobic organisms to have superoxide dismutase.

Accepted Answer

A) True 
 B)False

Question 12

Medically important bacteria are often

Accepted Answer

A) grown on agar containing blood. 
B) grown at 37°C. 
C) grown on agar containing chocolate. 
D) grown at a pH of 5. 
E) grown on agar containing blood AND grown at 37°C. 
A) grown on agar containing blood. 
B) grown at 37°C. 
C) grown on agar containing chocolate. 
D) grown at a pH of 5. 
E) grown on agar containing blood AND grown at 37°C.

Question 13

A physician sends a stool sample to your lab, and wants to know if there are lactose fermenting microbes in the sample. How might you determine if these microbes are present or not from this mixed-microbe specimen?

Accepted Answer

A) Streak the sample for isolation on Thayer-Martin agar (which contains lactose and particular antibiotics for selectivity). 
B) Streak the sample for isolation on a blood agar plate (which contains lactose AND red blood cells that enrich the culture for iron). 
C) Streak the sample for isolation on a MacConkey agar plate (which contains lactose and a pH indicator that turns pink when acid byproducts are present). 
D) None of the above would work-there's no way to reliably determine this feature from the specimen given. 
A) Streak the sample for isolation on Thayer-Martin agar (which contains lactose and particular antibiotics for selectivity). 
B) Streak the sample for isolation on a blood agar plate (which contains lactose AND red blood cells that enrich the culture for iron). 
C) Streak the sample for isolation on a MacConkey agar plate (which contains lactose and a pH indicator that turns pink when acid byproducts are present). 
D) None of the above would work-there's no way to reliably determine this feature from the specimen given.

Question 14

You are a microbiologist working for a pharmaceutical company and discover a new secreted metabolite that can serve as a medication. Your company asks you to oversee the production of the metabolite. Which of the following is something that is NOT important to consider if you need to grow 5,000 liter cultures of bacteria for the purpose of harvesting the metabolite they secrete?

Accepted Answer

A) The death rate of the bacteria after stationary phase is complete. 
B) The ideal rate of input of new nutrients into the culture to maintain the cells in log phase. 
C) The ideal rate of pulling off some of the culture in order to maintain the cells in log phase. 
D) The best way to mix the large vat in order to keep it homogenous (constant throughout) in terms of nutrients, temperature, and oxygen levels. 
E) The best way to keep the pH of the entire mixture at the ideal level to promote log phase growth. 
A) The death rate of the bacteria after stationary phase is complete. 
B) The ideal rate of input of new nutrients into the culture to maintain the cells in log phase. 
C) The ideal rate of pulling off some of the culture in order to maintain the cells in log phase. 
D) The best way to mix the large vat in order to keep it homogenous (constant throughout) in terms of nutrients, temperature, and oxygen levels. 
E) The best way to keep the pH of the entire mixture at the ideal level to promote log phase growth.

Question 15

Secondary metabolites may be antibiotics.

Accepted Answer

A) True 
 B)False

Question 16

Biofilms

Accepted Answer

A) are a haphazard mixture of bacteria. 
B) are a polysaccharide-encased community of microorganisms. 
C) may enhance bioremediation efforts. 
D) may protect organisms against harmful chemicals. 
E) are a polysaccharide-encased community of microorganisms, may enhance bioremediation efforts AND may protect organisms against harmful chemicals. 
A) are a haphazard mixture of bacteria. 
B) are a polysaccharide-encased community of microorganisms. 
C) may enhance bioremediation efforts. 
D) may protect organisms against harmful chemicals. 
E) are a polysaccharide-encased community of microorganisms, may enhance bioremediation efforts AND may protect organisms against harmful chemicals.

Question 17

The optimal temperature for most human pathogens might be expected to range from

Accepted Answer

A) 35-40°C. 
B) 20-45°C. 
C) 15-25°C. 
D) 93-98.6°C. 
A) 35-40°C. 
B) 20-45°C. 
C) 15-25°C. 
D) 93-98.6°C.

Question 18

The lag phase of the bacterial growth curve is marked by

Accepted Answer

A) a decrease in cell mass. 
B) dormant, metabolically inactive cells. 
C) metabolically active cells. 
D) vigorously dividing cells. 
A) a decrease in cell mass. 
B) dormant, metabolically inactive cells. 
C) metabolically active cells. 
D) vigorously dividing cells.

Question 19

You take absorbance readings on a spectrophotometer across a 6 hour culture of E. coli cells growing in tryptic soy broth (TSB). Your absorbance readings clearly indicate a lag phase, a log phase, and a stationary phase. You come back in and take readings at 8, 10, 12, 14, and 16 hours, but the absorbance number remains the same. Shouldn't it start coming down as the closed batch culture enters death phase? What's the most likely thing that is happening?

Accepted Answer

A) Clearly, something is wrong with the spectrophotometer and it isn't measuring the correct values.Perhaps something is on the detector, making it register falsely high absorbance numbers. 
B) When we establish a growth curve, we should actually plot the log of the number of viable cells vs.time.However, a spectrophotometer can only measure absorbance.Absorbance is NOT the same as the number of viable cells.Many of the cells in the tube are most likely dead, but the machine can't discriminate between a live cell and a dead one.This keeps the absorbance high even into the death phase. 
C) It'll happen-E.coli just grow slowly.We haven't gotten to the end of the stationary phase yet.Be patient! 
D) Perhaps there's a big smudge of something on the tube that is blocking some of the light.This would lead to an elevated reading for every timepoint after the smudge was placed on the tube. 
A) Clearly, something is wrong with the spectrophotometer and it isn't measuring the correct values.Perhaps something is on the detector, making it register falsely high absorbance numbers. 
B) When we establish a growth curve, we should actually plot the log of the number of viable cells vs.time.However, a spectrophotometer can only measure absorbance.Absorbance is NOT the same as the number of viable cells.Many of the cells in the tube are most likely dead, but the machine can't discriminate between a live cell and a dead one.This keeps the absorbance high even into the death phase. 
C) It'll happen-E.coli just grow slowly.We haven't gotten to the end of the stationary phase yet.Be patient! 
D) Perhaps there's a big smudge of something on the tube that is blocking some of the light.This would lead to an elevated reading for every timepoint after the smudge was placed on the tube.

Question 20

Freezing is an effective means of destroying bacteria.

Accepted Answer

A) True 
 B)False

Exam 4: Dynamics of Prokaryotic Growth

Organisms that are indifferent to the presence of oxygen and do not use it are

Organisms that require gaseous oxygen for metabolism are referred to as

A pure culture in exponential growth phase has a bacterial concentration of 6.4 x 108 cells/ml. If the bacterium has a generation time of 1 h, how long ago was the cell concentration 8.0 x 107 cells/ml?

The optimum pH for growth of most species of bacteria is

Agar replaced gelatin as the gelling (solidifying) agent for media because

High concentrations of salt and sugar in foods

A hot tub (approx. 104 deg. F or 40 deg. C) would most likely contain

The solidifying agent used most successfully in bacterial nutrient media is

During which phase of the bacterial growth curve does the total number of viable cells decline?

A urine sample with more than 100,000 organisms is considered indicative of infection. A urine sample containing 5,000 bacteria, with a generation time of 30 minutes, sits for 3 hours before finally being assayed. How many bacteria will then be present within the sample?

One would expect most strict anaerobic organisms to have superoxide dismutase.

Medically important bacteria are often

A physician sends a stool sample to your lab, and wants to know if there are lactose fermenting microbes in the sample. How might you determine if these microbes are present or not from this mixed-microbe specimen?

Secondary metabolites may be antibiotics.

Biofilms

The optimal temperature for most human pathogens might be expected to range from

The lag phase of the bacterial growth curve is marked by

Freezing is an effective means of destroying bacteria.

Humans and the Microbial World

The Molecules of Life

Microscopy and Cell Structure

Control of Microbial Growth

Metabolism: Fueling Cell Growth

The Blueprint of Life, From Dna to Protein

Bacterial Genetics

Biotechnology and Recombinant Dna

Identification and Classification of Prokaryotes

The Diversity of Prokaryotic Organisms

The Eukaryotic Members of the Microbial World

Viruses, Viroids and Prions

The Innate Immune Response

The Adaptive Immune Response

Host-Microbe Interactions

Immunologic Disorders

Applications of Immune Responses

Epidemiology

Antimicrobial Medications

Respiratory System Infections

Skin Infections

Wound Infections

Digestive System Infections

Genitourinary Infections

Nervous System Infections

Blood and Lymphatic Infections

Hiv Disease and Complications of Immunodeficiency

Microbial Ecology

Environmental Microbiology: Treatment of Water, Wastes, and Polluted Habitats

Food Microbiology

Filters

A pure culture in exponential growth phase has a bacterial concentration of 6.4 x 10⁸ cells/ml. If the bacterium has a generation time of 1 h, how long ago was the cell concentration 8.0 x 10⁷ cells/ml?