C5 Sample Questions from Brock

Question 1

Which of the following is/are transferred to daughter cells during bacterial cell division?
A) only genomic DNA, the blueprint for everything the cell needs
B) individual genes and enzymes to later be brought together to form the genome
C) only the chromosome and enzymes to immediately begin cellular metabolism
D) chromosome, proteins, and all other cellular constituents

Answer 1

D) chromosome, proteins, and all other cellular constituents

Bacterial cell division aims to create two functional daughter cells. This requires more than just DNA; it needs the entire cellular machinery including proteins, ribosomes, and other components.

Question 2

Bacterial growth refers to
A) an increase in the number of cells.
B) the occurrence of binary fission.
C) the time required for one cell to divide into two.
D) the occurrence of mitosis.

Answer 2

A) an increase in the number of cells.

Bacterial growth is defined by the increase in population size, specifically the number of cells, not the size of individual cells.

Question 3

The time interval required for the formation of two cells from one is called the
A) generation time.
B) growth time.
C) growth rate.
D) generation rate.

Answer 3

A) generation time.

Generation time is the time it takes for a population to double, representing the time for one cell to divide into two.

Question 4

The time between inoculation and the beginning of growth is usually called the
A) lag phase.
B) log phase.
C) dormant phase.
D) death phase.

Answer 4

A) lag phase.

The lag phase is the initial period after inoculation where cells adapt to the new environment before starting exponential growth.

Question 5

Bacteria that are able to grow in humans and cause disease would be classified as
A) psychrophiles.
B) mesophiles.
C) thermophiles.
D) hyperthermophiles.

Answer 5

B) mesophiles.

Human body temperature is around 37°C, which falls within the mesophilic range. Psychrophiles prefer cold temperatures, thermophiles prefer hot temperatures, and hyperthermophiles prefer extremely hot temperatures.

Question 6

The number of colonies obtained in a plate count does NOT depend on the
A) inoculum volume.
B) size of the colonies.
C) type of culture medium.
D) incubation time.

Answer 6

B) size of the colonies.

Colony size reflects growth rate and nutrient availability, not the initial number of viable cells. Inoculum volume, culture medium, and incubation time all affect the number of colonies.

Question 7

What temperature is most commonly used in autoclaves to sterilize growth media and other devices prior to experimentation?
A) 95°C
B) 101°C
C) 121°C
D) 140°C

Answer 7

C) 121°C

This temperature, combined with the pressure of 15 psi in an autoclave, is sufficient to kill most vegetative cells and endospores.

Question 8

Obligate anaerobes which are sensitive to O2 would be found growing
A) throughout a tube of thioglycolate broth.
B) only at the very top of a tube of thioglycolate broth.
C) only at the bottom of a tube of thioglycolate broth.
D) approximately one-third of the way down the thioglycolate broth.

Answer 8

C) only at the bottom of a tube of thioglycolate broth.

Obligate anaerobes are sensitive to oxygen and will grow where oxygen is absent, which is at the bottom of the thioglycolate broth tube.

Question 9

Which of these statements is/are TRUE?
A) In general, species that can grow at higher temperatures are prokaryotic.
B) The most thermophilic prokaryotes are species of Archaea.
C) Chemoorganotrophic organisms are able to grow at higher temperatures than phototrophic organisms.
D) All of the statements are true.

Answer 9

D) All of the statements are true.

Prokaryotes generally have higher temperature tolerances than eukaryotes. Archaea hold the record for the most thermophilic organisms. Chemoorganotrophs can also inhabit higher temperature niches than phototrophs.

Question 10

A chemical that denatures proteins is most likely to be classified as a(n) _______ agent.
A) antiseptic
B) bacteriostatic
C) bactericidal
D) detergent

Answer 10

C) bactericidal.

Denaturing proteins disrupts essential cellular functions, leading to cell death. Bactericidal agents kill bacteria.

Question 11

Organisms able to live in environments with high sugar concentrations are
A) halotolerant.
B) osmophiles.
C) xerophiles.
D) anaerobic fermenting bacteria.

Answer 11

B) osmophiles.

Osmophiles thrive in environments with high osmotic pressure, such as high sugar concentrations.

Question 12

Which term is most relevant in describing the efficacy of an antimicrobial for use in a clinical setting?
A) effective dose
B) sterilization coefficient
C) lethal dosage
D) minimum inhibitory concentration (MIC)

Answer 12

D) minimum inhibitory concentration (MIC)

MIC is the lowest concentration of an antimicrobial that inhibits visible growth, a crucial factor in clinical settings.

Question 13

When counting colonies on an agar plate
A) it is assumed that each colony arose from division of one or a few cells.
B) only viable colonies are counted.
C) the medium must be suitable for colony growth.
D) All of these answer choices are true.

Answer 13

D) All of these answer choices are true.

These are fundamental assumptions and requirements of the plate count method.

Question 14

The optimal growth temperature of a bacterium is most closely related to the optimal temperature for
A) transcription of DNA.
B) DNA replication.
C) enzyme function.
D) mRNA attachment to ribosomes.

Answer 14

C) enzyme function.

Enzyme activity is highly temperature-dependent, and the optimal growth temperature usually corresponds to the optimal temperature for enzyme function.

Question 15

Why is the enzyme catalase important to the survival of bacteria?
A) Catalase protects the cell from desiccation.
B) Catalase breaks down toxic hydrogen peroxide.
C) Catalase allows for growth in high salt concentrations.
D) Catalase aids in the transport of oxygen into the cell.

Answer 15

B) Catalase breaks down toxic hydrogen peroxide.

Hydrogen peroxide is a byproduct of aerobic metabolism and is toxic to cells. Catalase neutralizes it.

Question 16

A medium containing known substance in precise amounts is known as a _______ media.
A) selective
B) complex
C) natural
D) defined

Answer 16

D) defined

Defined media have precisely known compositions.

Question 17

Selective medium differs from differential medium because
A) selective medium permits growth of more organisms than differential medium.
B) selective medium permits growth of a particular microbial type while differential medium is used to distinguish between types of organisms.
C) differential medium differentiates pathogens from nonpathogens while selective medium grows only pathogens.
D) differential medium contains growth inhibitors while selective medium does not.

Answer 17

B) selective medium permits growth of a particular microbial type while differential medium is used to distinguish between types of organisms.

Selective media inhibit unwanted microbes, while differential media distinguish between different types based on observable characteristics.

Question 18

The use of chemical agents directly on exposed body surfaces to destroy or inhibit vegetative pathogens is
A) disinfection.
B) sterilization.
C) antisepsis.
D) sanitization.

Answer 18

C) antisepsis.

Antisepsis refers to using antimicrobial agents on living tissue.

Question 19

Which of the following statements is TRUE of disinfectants?
A) They are always effective in destroying endospores.
B) They are used on living tissue.
C) They are used for sterilization.
D) They are used on inanimate surfaces.

Answer 19

D) They are used on inanimate surfaces.

Disinfectants are used on non-living surfaces. Antiseptics are used on living tissue.

Question 20

A ______ agent is a chemical that inhibits bacteria from reproducing, but does NOT necessarily kill them.
A) bacteriostatic
B) bacteriolytic
C) bactericidal
D) xerophilic

Answer 20

A) bacteriostatic

Bacteriostatic agents inhibit growth but don’t necessarily kill.

Question 21

Microbial contamination is prevented by the
A) use of the quadrant streak method.
B) use of aseptic technique.
C) use of cultures containing special nutrients.
D) spread plate method.

Answer 21

B) use of aseptic technique.

Aseptic technique prevents microbial contamination.

Question 22

A common antimicrobial chemical (or chemicals) used as both an antiseptic and a general disinfectant is
A) iodophors.
B) 70% alcohol.
C) hydrogen peroxide.
D) Each of these chemicals at appropriate concentrations can be used as antiseptics or disinfectants.

Answer 22

D) Each of these chemicals at appropriate concentrations can be used as antiseptics or disinfectants.

The concentration and application determine whether these chemicals are used as antiseptics or disinfectants.

Question 23

Cultures of a bacterial species were incubated on the shelf of a refrigerator (5°C), on a lab benchtop (25°C), on the shelf of a 37°C incubator, and on the shelf of a 50°C incubator. After incubation, there was no growth at 37°C or 50°C, slight growth on the benchtop, and abundant growth at refrigeration. What term could be used for this species?
A) halophile
B) mesophile
C) anaerobe
D) psychrophile

Answer 23

D) psychrophile

Growth at refrigeration temperature (5°C) and lack of growth at higher temperatures indicate a psychrophile.

Question 24

T/F: Microbial growth is generally described as an increase in cell number rather than the expansion in size of an individual microbial cell.

Answer 24

True. Growth is measured by an increase in cell numbers.

Question 25

T/F: The duration of exponential growth would increase if bacterial cells divided into three equal daughter cells rather than two.

Answer 25

False. If cells divided into three, the population would increase faster, shortening the exponential growth phase.

Question 26

T/F: A selective medium is used to suppress the growth of certain bacteria in order to facilitate the growth of other bacteria.

Answer 26

True. Selective media favor the growth of specific microorganisms by inhibiting others.

Question 27

T/F: The rate of exponential growth varies greatly according to bacterial species and bioavailable nutrients.

Answer 27

True. Growth rates are influenced by species-specific characteristics and nutrient availability.

Question 28

T/F: A bacterium whose optimal growth temperature is 35˚C would be classified as a thermophile.

Answer 28

False. A thermophile has an optimal growth temperature significantly higher than 35°C. 35°C would classify the organism as a mesophile.

Question 29

T/F: A complex medium is one that has been completely made in the laboratory and the concentration of all the nutrients is known.

Answer 29

False. A defined medium has a known composition. A complex medium contains components whose exact composition is undefined (e.g., yeast extract).

Question 30

T/F: Direct microscopic counting of cells is an accurate method for estimating the number of viable cells in a sample.

Answer 30

False. Direct counts include both live and dead cells. Viable counts are needed to estimate the number of living cells.

Question 31

T/F: Refrigeration controls microbial growth in food as a result of irreversible cell damage caused by low temperature.

Answer 31

False. Refrigeration slows or inhibits microbial growth, primarily by slowing enzymatic activity. It doesn’t necessarily cause irreversible damage.

Question 32

T/F: The optimum growth temperature for an organism is typically closer to its minimum temperature rather than the maximum temperature.

Answer 32

False. The optimum growth temperature is usually closer to the maximum than the minimum.

Question 33

T/F: Knowledge of microbial growth patterns is useful in working with the control of microbial growth.

Answer 33

True. Understanding microbial growth is crucial for controlling their growth in various settings.

Question 34

T/F: Autoclaving and pasteurization are two processes that are both very effective for sterilization.

Answer 34

False. Autoclaving sterilizes, but pasteurization only reduces microbial load.

Question 35

T/F: Sterility of a laminar flow hood is accomplished by filter-sterilized air passed through the hood quickly enough that non-sterile air does not flow into the work area.

Answer 35

True. Laminar flow hoods use HEPA filters and airflow to maintain a sterile work area.