Question 1

Medically important bacteria are often

Accepted Answer

A)  grown on agar containing blood AND grown at 4°C. 
B)  grown at 37°C AND grown at a pH of 5. 
C)  grown on agar containing blood AND grown at 37°C. 
D)  grown on agar containing chocolate AND grown at 4°C. 
E)  grown at a pH of 5 AND grown at 4°C. 
A)  grown on agar containing blood AND grown at 4°C. 
B)  grown at 37°C AND grown at a pH of 5. 
C)  grown on agar containing blood AND grown at 37°C. 
D)  grown on agar containing chocolate AND grown at 4°C. 
E)  grown at a pH of 5 AND grown at 4°C.

Question 2

In microbiology, growth usually refers to an increase in size of the bacteria.

Accepted Answer

A) True 
 B)False

Question 3

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)  Either Thayer-Martin agar or blood agar would work, as long as the plates are incubated in an anaerobic chamber. 
E)  None of the answer choices 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)  Either Thayer-Martin agar or blood agar would work, as long as the plates are incubated in an anaerobic chamber. 
E)  None of the answer choices would work-there's no way to reliably determine this feature from the specimen given.

Question 4

A medium that inhibits the growth of organisms other than the one being sought is called a(n)

Accepted Answer

A)  synthetic medium. 
B)  specific culture medium. 
C)  selective medium. 
D)  enrichment medium. 
E)  differential medium. 
A)  synthetic medium. 
B)  specific culture medium. 
C)  selective medium. 
D)  enrichment medium. 
E)  differential medium.

Question 5

A cluster of cases of legionellosis have occurred in your neighborhood. People with the illness have cough, fever, shortness of breath, chest pain and sometimes diarrhea. The illness is caused by the bacterium Legionella pneumophila, a facultative intracellular parasite that survives in certain ameba. The organism has an absolute requirement for L-cysteine.
-A modification of the BCYE medium used to culture L. pneumophila is BCYE with DGVP. This medium contains glycine, polymixin B (an antifungal agent), and and vancomycin (antibiotic), as well as two dyes (bromocreson purple and bromthymol blue) that facilitate identification of the organism based on colony color. What type of medium is BCYE with DGVP?

Accepted Answer

A)  Selective 
B)  Differential 
C)  Selective AND differential 
D)  Liquid 
E)  Anaerobic 
A)  Selective 
B)  Differential 
C)  Selective AND differential 
D)  Liquid 
E)  Anaerobic

Question 6

Trace elements

Accepted Answer

A)  include zinc, copper, and manganese AND may be needed for enzyme function. 
B)  include zinc, copper, and manganese AND are required in large amounts. 
C)  may be needed for enzyme function AND are involved in maintaining pH in the cell. 
D)  are required in large amounts AND may be needed for enzyme function. 
E)  are involved in maintaining pH in the cell AND include zinc, copper, and manganese. 
A)  include zinc, copper, and manganese AND may be needed for enzyme function. 
B)  include zinc, copper, and manganese AND are required in large amounts. 
C)  may be needed for enzyme function AND are involved in maintaining pH in the cell. 
D)  are required in large amounts AND may be needed for enzyme function. 
E)  are involved in maintaining pH in the cell AND include zinc, copper, and manganese.

Question 7

In addition to the few Shigella colonies that are noted, there are also abundant salmon pink colonies, around which the medium has turned yellow, losing its original blue color. You know that hektoen enteric agar must contain ________.

Accepted Answer

A)  lactose 
B)  a pH indicator 
C)  a weak acid 
D)  malachite green 
E)  penicillin 
A)  lactose 
B)  a pH indicator 
C)  a weak acid 
D)  malachite green 
E)  penicillin

Question 8

MacConkey agar is

Accepted Answer

A)  a selective medium. 
B)  a selective and differential medium. 
C)  a differential medium. 
D)  an enrichment medium. 
E)  an anaerobic medium. 
A)  a selective medium. 
B)  a selective and differential medium. 
C)  a differential medium. 
D)  an enrichment medium. 
E)  an anaerobic medium.

Question 9

When doing experiments with bacteria,

Accepted Answer

A)  it is usually not necessary to standardize which stage of growth is used. 
B)  it is best to use colonies, as all the bacteria in a colony are at the same stage of growth. 
C)  it is best to use bacteria from the same stage of growth. 
D)  the age of the bacteria is not important. 
E)  it is best to use mixed populations and biofilms. 
A)  it is usually not necessary to standardize which stage of growth is used. 
B)  it is best to use colonies, as all the bacteria in a colony are at the same stage of growth. 
C)  it is best to use bacteria from the same stage of growth. 
D)  the age of the bacteria is not important. 
E)  it is best to use mixed populations and biofilms.

Question 10

A cluster of cases of legionellosis have occurred in your neighborhood. People with the illness have cough, fever, shortness of breath, chest pain and sometimes diarrhea. The illness is caused by the bacterium Legionella pneumophila, a facultative intracellular parasite that survives in certain ameba. The organism has an absolute requirement for L-cysteine.
-Diagnosis of legionellosis depends partly on culture of the causative agent from medical samples. Typically, the organism is grown on buffered charcoal yeast extract (BCYE) agar. What essential component must this medium have to ensure growth of L. pneumophila?

Accepted Answer

A)  red blood cells 
B)  chlorine 
C)  NaCl 
D)  cysteine 
E)  All of the answer choices are correct. 
A)  red blood cells 
B)  chlorine 
C)  NaCl 
D)  cysteine 
E)  All of the answer choices are correct.

Question 11

Candle jars are usually used to

Accepted Answer

A)  prevent candles from melting. 
B)  provide an atmosphere with CO₂. 
C)  stimulate the growth of obligate anaerobes. 
D)  prevent the growth of obligate aerobes. 
E)  enhance the growth of microaerophiles. 
A)  prevent candles from melting. 
B)  provide an atmosphere with CO₂. 
C)  stimulate the growth of obligate anaerobes. 
D)  prevent the growth of obligate aerobes. 
E)  enhance the growth of microaerophiles.

Question 12

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)  Something is likely 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)  A spectrophotometer can measure absorbance as an indicator of cell number, but can't discriminate between a live cell and a dead one. The presence of dead cells keeps the absorbance high even into the death phase. 
C)  E. coli just grows slowly, and has a long generation time. After 16 hours the cells are still in stationary phase, so the cell numbers are expectedly constant. 
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. 
E)  There is no point in measuring the absorbance of the culture because the cells are bacterial. It would make more sense to measure would the transmission value. 
A)  Something is likely 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)  A spectrophotometer can measure absorbance as an indicator of cell number, but can't discriminate between a live cell and a dead one. The presence of dead cells keeps the absorbance high even into the death phase. 
C)  E. coli just grows slowly, and has a long generation time. After 16 hours the cells are still in stationary phase, so the cell numbers are expectedly constant. 
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. 
E)  There is no point in measuring the absorbance of the culture because the cells are bacterial. It would make more sense to measure would the transmission value.

Question 13

A microbe is discovered growing near a deep sea thermal vent. When researchers bring a sample up to the surface and try to grow it in a lab at room temperature in a normal incubator, they are unsuccessful. Why?

Accepted Answer

A)  The pressure isn't the same at sea level as it is on the ocean floor and the microbe may require a very specific pressure. 
B)  Oxygen concentrations are very different between the two environments-it's possible the microbe is a strict anaerobe and is poisoned by the air (oxygen) in the lab. 
C)  Salt concentrations might be different in the media the researchers are attempting to use and the salt water the microbe is used to living in. This might be causing osmotic pressure differences that the microbe can't tolerate. 
D)  The temperature is probably different-the thermal vent would be very hot, while these researchers are trying to grow this microbe at room temperature. 
E)  All of the answer choices are correct. 
A)  The pressure isn't the same at sea level as it is on the ocean floor and the microbe may require a very specific pressure. 
B)  Oxygen concentrations are very different between the two environments-it's possible the microbe is a strict anaerobe and is poisoned by the air (oxygen) in the lab. 
C)  Salt concentrations might be different in the media the researchers are attempting to use and the salt water the microbe is used to living in. This might be causing osmotic pressure differences that the microbe can't tolerate. 
D)  The temperature is probably different-the thermal vent would be very hot, while these researchers are trying to grow this microbe at room temperature. 
E)  All of the answer choices are correct.

Question 14

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

Accepted Answer

A)  Stationary 
B)  Lag 
C)  Exponential 
D)  Death 
E)  Infection 
A)  Stationary 
B)  Lag 
C)  Exponential 
D)  Death 
E)  Infection

Question 15

All the bacterial cells that result from the replication of a single original bacterial organism are referred to as a

Accepted Answer

A)  mixed population. 
B)  pure culture. 
C)  lag culture. 
D)  mutant culture. 
E)  single culture. 
A)  mixed population. 
B)  pure culture. 
C)  lag culture. 
D)  mutant culture. 
E)  single culture.

Question 16

The scientist that contributed most to the development of pure culture techniques was

Accepted Answer

A)  Alexander Fleming. 
B)  Louis Pasteur. 
C)  Edward Jenner. 
D)  Robert Koch. 
E)  Paul Ehrlich. 
A)  Alexander Fleming. 
B)  Louis Pasteur. 
C)  Edward Jenner. 
D)  Robert Koch. 
E)  Paul Ehrlich.

Question 17

If you are asked to make 200 mL of Thayer-Martin agar, who much sheep's blood would you add to the medium? Recall that this complex medium contains 5% sheep blood.

Accepted Answer

A)  10% 
B)  5 mL 
C)  10 mL 
D)  Random quantities 
E)  10,000 RBCs 
A)  10% 
B)  5 mL 
C)  10 mL 
D)  Random quantities 
E)  10,000 RBCs

Question 18

A cluster of cases of legionellosis have occurred in your neighborhood. People with the illness have cough, fever, shortness of breath, chest pain and sometimes diarrhea. The illness is caused by the bacterium Legionella pneumophila, a facultative intracellular parasite that survives in certain ameba. The organism has an absolute requirement for L-cysteine.
-L. pneumophila is widespread and is found in various water sources, including hot tubs, water cooling towers, swimming pools, grocery store misters, and shower water. Select the False statement  regarding the organism, given this information.

Accepted Answer

A)  It survives in the presence of chlorine. 
B)  It is a mesophile. 
C)  It is an obligate anaerobe. 
D)  It can survive in water pipes. 
E)  It is a mesophile AND it can survive the presence of chlorine. 
A)  It survives in the presence of chlorine. 
B)  It is a mesophile. 
C)  It is an obligate anaerobe. 
D)  It can survive in water pipes. 
E)  It is a mesophile AND it can survive the presence of chlorine.

Question 19

Clostridium paradoxum grows optimally at 55°C, pH 9.3; it will not grow in the presence of O₂. Please select the True statement about this organism.

Accepted Answer

A)  It is spherical in shape. 
B)  It is a psychrophile. 
C)  It is an obligate anaerobe. 
D)  It is an acidophile. 
E)  It is an aerotolerant anaerobe. 
A)  It is spherical in shape. 
B)  It is a psychrophile. 
C)  It is an obligate anaerobe. 
D)  It is an acidophile. 
E)  It is an aerotolerant anaerobe.

Question 20

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 
E)  pH 1 
A)  pH 5 
B)  pH 7 
C)  pH 9 
D)  pH 6 
E)  pH 1

Exam 4: Dynamics of Microbial Growth

Medically important bacteria are often

In microbiology, growth usually refers to an increase in size of the bacteria.

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?

A medium that inhibits the growth of organisms other than the one being sought is called a(n)

Trace elements

In addition to the few Shigella colonies that are noted, there are also abundant salmon pink colonies, around which the medium has turned yellow, losing its original blue color. You know that hektoen enteric agar must contain ________.

MacConkey agar is

When doing experiments with bacteria,

Candle jars are usually used to

A microbe is discovered growing near a deep sea thermal vent. When researchers bring a sample up to the surface and try to grow it in a lab at room temperature in a normal incubator, they are unsuccessful. Why?

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

All the bacterial cells that result from the replication of a single original bacterial organism are referred to as a

The scientist that contributed most to the development of pure culture techniques was

If you are asked to make 200 mL of Thayer-Martin agar, who much sheep's blood would you add to the medium? Recall that this complex medium contains 5% sheep blood.

Clostridium paradoxum grows optimally at 55°C, pH 9.3; it will not grow in the presence of O₂. Please select the True statement about this organism.

The optimum pH for growth of most species of bacteria is ________.

Humans and the Microbial World

The Molecules of Life

Microscopy and Cell Structure

Control of Microbial Growth

Microbial Metabolism: Fueling Cell Growth

The Blueprint of Life, from DNA to Protein

Bacterial Genetics

Biotechnology

Identifying and Classifying Microorganisms

The Diversity of Bacteria and Archaea

The Eukaryotic Members of the Microbial World

Viruses, Viroids, and Prions

The Innate Immune Response

The Adaptive Immune Response

Host-Microbe Interactions

Immunological Disorders

Applications of Immune Responses

Epidemiology

Antimicrobial Medications

Respiratory System Infections

Skin Infections

Wound Infections

Digestive System Infections

Blood and Lymphatic Infections

Nervous System Infections

Genitourinary Tract Infections

Microbial Ecology

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

Food Microbiology

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