Microbiology (Tortora 12th edition)
Chapter 6, 7, 10, 11, 12 Test bank
Quizzes All Solved 2025-2026 Updated.
If cells are grown in media containing amino acids labeled with radioactive nitrogen (15N), most
of the radioactivity will be found in the cells - Answer DNA and proteins.
Which of the following elements is NOT correctly matched with its cellular function? - Answer
phosphorus used for production of carbohydrates
Pathogenic bacteria isolated from the respiratory or intestinal tracts of humans are - Answer
capnophiles that grow best in carbon dioxide incubators.
The biosafety level (BSL) for most introductory microbiology laboratories is - Answer BSL-1.
The biosafety level (BSL) for a clinical microbiology laboratory working with potentially airborne
pathogens, such as tuberculosis bacteria, is - Answer BSL-3.
A sample of milk is tested for its bacterial content in a plate count assay. A one-milliliter sample
of the milk is diluted in a 1:10 dilution series. One milliliter of the third dilution tube is plated in
a pour plate. After incubation, the plate has 54 colonies, indicating that the original milk sample
contained - Answer 54,000 cells per milliliter.
The addition of which of the following to a culture medium will neutralize acids? - Answer
buffers
Salts and sugars work to preserve foods by creating a - Answer hypertonic environment.
The term aerotolerant anaerobe refers to an organism that - Answer does not use oxygen
but tolerates it.
Which of the following is an advantage of the standard plate count? - Answer determines
the number of viable cells
,Thirty-six colonies grew in nutrient agar from 1.0 ml of undiluted sample in a standard plate
count. How many cells were in the original sample? - Answer 36 per milliliter
Most bacteria grow best at pH - Answer 7
Most fungi grow best at pH - Answer 5
Consider a culture medium on which only gram-positive organisms such as Staphylococcus
aureus colonies can grow due to an elevated NaCl level. A yellow halo surrounds the growth,
indicating the bacterium fermented a sugar in the medium, decreasing the pH as a result and
changing the color of a pH indicator chemical. This type of medium would be referred to as a(n)
- Answer selective and differential medium.
A culture medium consisting of agar, peptone, and beef heart is a - Answer complex medium
Which of the following pairs of microbe classification terms and optimal growth temperatures is
mismatched? - Answer thermophile growth at 37C
During which growth phase will gram-positive bacteria be most susceptible to penicillin? -
Answer log phase
Which of the following is the best definition of generation time? - Answer the length of time
needed for a cell to divide
Which of the following is NOT a direct method to measure microbial growth? - Answer
metabolic activity
Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt? -
Answer facultative halophiles
Which of the following is an organic growth factor? - Answer vitamin B1
Which of the following is an example of a metabolic activity that could be used to measure
microbial growth? - Answer glucose consumption
, Three cells with generation times of 60 minutes are inoculated into a culture medium. How
many cells are there after 5 hours? - Answer 96
In one hospital, Pseudomonas aeruginosa serotype 10 infected the biliary tract of 10 percent of
1300 patients who underwent gastrointestinal endoscopic procedures. After each use,
endoscopes were washed with an automatic reprocessor that flushed detergent and
glutaraldehyde through the endoscopes, followed by a tap water rinse. P. aeruginosa serotype
10 was not isolated from the detergent, glutaraldehyde, or tap water. What was the source of
the infections? - Answer a biofilm in the reprocessor
Assume you inoculated 100 cells, with a generation time of 20 minutes, into 100 ml of nutrient
broth. You then inoculated 100 cells of the same species into 200 ml of nutrient broth. After
incubation for 4 hours, you can reasonably expect to have - Answer the same number of
cells in both.
The source of nutrients in nutrient agar is - Answer peptone and beef extract.
Which enzyme catalyzes the reaction: O2 + O2 + 2H+ H2O2 + O2? - Answer superoxide
dismutase
Which enzyme catalyzes the reaction: 2H2O2 2H2O + O2? - Answer catalase
Which enzyme catalyzes the reaction: H2O2 + 2H+ 2H2O? - Answer peroxidase
Patients with indwelling catheters (long-term tubes inserted into body orifices for drainage,
such as through the urethra and into the urinary bladder) are susceptible to infections because -
Answer biofilms develop on catheters.
An isolated colony on a streak plate contains millions (or even billions) of identical cells all
arising from one initial cell. - Answer TRUE
Bacterial growth refers to an increase in the numbers of cells in a bacterial culture. - Answer
TRUE
Pure cultures can easily be obtained on streak plates, even if the desired bacteria are present in
very low concentrations in the initial culture broth. - Answer FALSE
Chapter 6, 7, 10, 11, 12 Test bank
Quizzes All Solved 2025-2026 Updated.
If cells are grown in media containing amino acids labeled with radioactive nitrogen (15N), most
of the radioactivity will be found in the cells - Answer DNA and proteins.
Which of the following elements is NOT correctly matched with its cellular function? - Answer
phosphorus used for production of carbohydrates
Pathogenic bacteria isolated from the respiratory or intestinal tracts of humans are - Answer
capnophiles that grow best in carbon dioxide incubators.
The biosafety level (BSL) for most introductory microbiology laboratories is - Answer BSL-1.
The biosafety level (BSL) for a clinical microbiology laboratory working with potentially airborne
pathogens, such as tuberculosis bacteria, is - Answer BSL-3.
A sample of milk is tested for its bacterial content in a plate count assay. A one-milliliter sample
of the milk is diluted in a 1:10 dilution series. One milliliter of the third dilution tube is plated in
a pour plate. After incubation, the plate has 54 colonies, indicating that the original milk sample
contained - Answer 54,000 cells per milliliter.
The addition of which of the following to a culture medium will neutralize acids? - Answer
buffers
Salts and sugars work to preserve foods by creating a - Answer hypertonic environment.
The term aerotolerant anaerobe refers to an organism that - Answer does not use oxygen
but tolerates it.
Which of the following is an advantage of the standard plate count? - Answer determines
the number of viable cells
,Thirty-six colonies grew in nutrient agar from 1.0 ml of undiluted sample in a standard plate
count. How many cells were in the original sample? - Answer 36 per milliliter
Most bacteria grow best at pH - Answer 7
Most fungi grow best at pH - Answer 5
Consider a culture medium on which only gram-positive organisms such as Staphylococcus
aureus colonies can grow due to an elevated NaCl level. A yellow halo surrounds the growth,
indicating the bacterium fermented a sugar in the medium, decreasing the pH as a result and
changing the color of a pH indicator chemical. This type of medium would be referred to as a(n)
- Answer selective and differential medium.
A culture medium consisting of agar, peptone, and beef heart is a - Answer complex medium
Which of the following pairs of microbe classification terms and optimal growth temperatures is
mismatched? - Answer thermophile growth at 37C
During which growth phase will gram-positive bacteria be most susceptible to penicillin? -
Answer log phase
Which of the following is the best definition of generation time? - Answer the length of time
needed for a cell to divide
Which of the following is NOT a direct method to measure microbial growth? - Answer
metabolic activity
Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt? -
Answer facultative halophiles
Which of the following is an organic growth factor? - Answer vitamin B1
Which of the following is an example of a metabolic activity that could be used to measure
microbial growth? - Answer glucose consumption
, Three cells with generation times of 60 minutes are inoculated into a culture medium. How
many cells are there after 5 hours? - Answer 96
In one hospital, Pseudomonas aeruginosa serotype 10 infected the biliary tract of 10 percent of
1300 patients who underwent gastrointestinal endoscopic procedures. After each use,
endoscopes were washed with an automatic reprocessor that flushed detergent and
glutaraldehyde through the endoscopes, followed by a tap water rinse. P. aeruginosa serotype
10 was not isolated from the detergent, glutaraldehyde, or tap water. What was the source of
the infections? - Answer a biofilm in the reprocessor
Assume you inoculated 100 cells, with a generation time of 20 minutes, into 100 ml of nutrient
broth. You then inoculated 100 cells of the same species into 200 ml of nutrient broth. After
incubation for 4 hours, you can reasonably expect to have - Answer the same number of
cells in both.
The source of nutrients in nutrient agar is - Answer peptone and beef extract.
Which enzyme catalyzes the reaction: O2 + O2 + 2H+ H2O2 + O2? - Answer superoxide
dismutase
Which enzyme catalyzes the reaction: 2H2O2 2H2O + O2? - Answer catalase
Which enzyme catalyzes the reaction: H2O2 + 2H+ 2H2O? - Answer peroxidase
Patients with indwelling catheters (long-term tubes inserted into body orifices for drainage,
such as through the urethra and into the urinary bladder) are susceptible to infections because -
Answer biofilms develop on catheters.
An isolated colony on a streak plate contains millions (or even billions) of identical cells all
arising from one initial cell. - Answer TRUE
Bacterial growth refers to an increase in the numbers of cells in a bacterial culture. - Answer
TRUE
Pure cultures can easily be obtained on streak plates, even if the desired bacteria are present in
very low concentrations in the initial culture broth. - Answer FALSE
