Exam 2 - Chapter 9 Book+HW/Quizzes

Question 1

Which of the following methods would be used to measure the concentration of bacterial contamination in processed peanut butter?
turbidity measurement
total plate count
dry weight measurement
direct counting of bacteria on a calibrated slide under the microscope

Answer 1

total plate count

Question 2

In which phase would you expect to observe the most endospores in a Bacillus cell culture?
death phase
lag phase
log phase
log, lag, and death phases would all have roughly the same number of endospores.

Answer 2

death phase

Question 3

During which phase would penicillin, an antibiotic that inhibits cell-wall synthesis, be most effective?
death phase
lag phase
log phase
stationary phase

Answer 3

log phase

Question 4

Which of the following is the best definition of generation time in a bacterium?
the length of time it takes to reach the log phase
the length of time it takes for a population of cells to double
the time it takes to reach stationary phase
the length of time of the exponential phase

Answer 4

the length of time it takes for a population of cells to double

Question 5

What is the function of the Z ring in binary fission?
It controls the replication of DNA.
It forms a contractile ring at the septum.
It separates the newly synthesized DNA molecules.
It mediates the addition of new peptidoglycan subunits.

Answer 5

It forms a contractile ring at the septum.

Question 6

If a culture starts with 50 cells, how many cells will be present after five generations with no cell death?
200
400
1600
3200

Answer 6

1600

Question 7

Filamentous cyanobacteria often divide by which of the following?
budding
mitosis
fragmentation
formation of endospores

Answer 7

fragmentation

Question 8

. Which is a reason for antimicrobial resistance being higher in a biofilm than in free-floating bacterial cells?
The EPS allows faster diffusion of chemicals in the biofilm.
Cells are more metabolically active at the base of a biofilm.
Cells are metabolically inactive at the base of a biofilm.
The structure of a biofilm favors the survival of antibiotic resistant cells.

Answer 8

Cells are metabolically inactive at the base of a biofilm.

Question 9

Quorum sensing is used by bacterial cells to determine which of the following?
the size of the population
the availability of nutrients
the speed of water flow
the density of the population

Answer 9

the density of the population

Question 10

. Which of the following statements about autoinducers is incorrect?
They bind directly to DNA to activate transcription.
They can activate the cell that secreted them.
N-acylated homoserine lactones are autoinducers in gram-negative cells.
Autoinducers may stimulate the production of virulence factors.

Answer 10

They bind directly to DNA to activate transcription.

Question 11

An inoculated thioglycolate medium culture tube shows dense growth at the surface and turbidity throughout the rest of the tube. What is your conclusion?
The organisms die in the presence of oxygen
The organisms are facultative anaerobes.
The organisms should be grown in an anaerobic chamber.
The organisms are obligate aerobes.

Answer 11

The organisms are facultative anaerobes.

Question 12

An inoculated thioglycolate medium culture tube is clear throughout the tube except for dense growth at the bottom of the tube. What is your conclusion?
The organisms are obligate anaerobes.
The organisms are facultative anaerobes.
The organisms are aerotolerant.
The organisms are obligate aerobes.

Answer 12

The organisms are obligate anaerobes.

Question 13

Pseudomonas aeruginosa is a common pathogen that infects the airways of patients with cystic fibrosis. It does not grow in the absence of oxygen. The bacterium is probably which of the following?
an aerotolerant anaerobe
an obligate aerobe
an obligate anaerobe
a facultative anaerobe

Answer 13

an obligate aerobe

Question 14

Streptococcus mutans is a major cause of cavities. It resides in the gum pockets, does not have catalase activity, and can be grown outside of an anaerobic chamber. The bacterium is probably which of the following?
a facultative anaerobe
an obligate aerobe
an obligate anaerobe
an aerotolerant anaerobe

Answer 14

an aerotolerant anaerobe

Question 15

Why do the instructions for the growth of Neisseria gonorrhoeae recommend a CO2-enriched atmosphere?
It uses CO2 as a final electron acceptor in respiration.
It is an obligate anaerobe.
It is a capnophile.
It fixes CO2 through photosynthesis.

Answer 15

It is a capnophile.

Question 16

. Bacteria that grow in mine drainage at pH 1–2 are probably which of the following?
alkaliphiles
acidophiles
neutrophiles
obligate anaerobes

Answer 16

acidophiles

Question 17

Bacteria isolated from Lake Natron, where the water pH is close to 10, are which of the following?
alkaliphiles
facultative anaerobes
neutrophiles
obligate anaerobes

Answer 17

alkaliphiles

Question 18

. In which environment are you most likely to encounter an acidophile?
human blood at pH 7.2
a hot vent at pH 1.5
human intestine at pH 8.5
milk at pH 6.5

Answer 18

a hot vent at pH 1.5

Question 19

A soup container was forgotten in the refrigerator and shows contamination. The contaminants are probably which of the following?
thermophiles
acidophiles
mesophiles
psychrotrophs

Answer 19

psychrotrophs

Question 20

Bacteria isolated from a hot tub at 39 °C are probably which of the following?
thermophiles
psychrotrophs
mesophiles
hyperthermophiles

Answer 20

mesophiles

Question 21

In which environment are you most likely to encounter a hyperthermophile?
hot tub
warm ocean water in Florida
hydrothermal vent at the bottom of the ocean
human body

Answer 21

hydrothermal vent at the bottom of the ocean

Question 22

Which of the following environments would harbor psychrophiles?
mountain lake with a water temperature of 12 °C
contaminated plates left in a 35 °C incubator
yogurt cultured at room temperature
salt pond in the desert with a daytime temperature of 34 °C

Answer 22

mountain lake with a water temperature of 12 °C

Question 23

Which of the following is the reason jams and dried meats often do not require refrigeration to prevent spoilage?
low pH
toxic alkaline chemicals
naturally occurring antibiotics
low water activity

Answer 23

low water activity

Question 24

Bacteria living in salt marshes are most likely which of the following?
acidophiles
barophiles
halotolerant
thermophiles

Answer 24

halotolerant

Question 25

EMB agar is a medium used in the identification and isolation of pathogenic bacteria. It contains digested meat proteins as a source of organic nutrients. Two indicator dyes, eosin and methylene blue, inhibit the growth of gram-positive bacteria and distinguish between lactose fermenting and nonlactose fermenting organisms. Lactose fermenters form metallic green or deep purple colonies, whereas the nonlactose fermenters form completely colorless colonies. EMB agar is an example of which of the following?
a selective medium only
a differential medium only
a selective medium and a chemically defined medium
a selective medium, a differential medium, and a complex medium

Answer 25

a selective medium, a differential medium, and a complex medium

Question 26

Haemophilus influenzae must be grown on chocolate agar, which is blood agar treated with heat to release growth factors in the medium. H. influenzae is described as ________.
an acidophile
a thermophile
an obligate anaerobe
fastidious

Answer 26

fastidious

Question 27

Capnophiles are bacteria that grow best under which of the following conditions?

relatively high CO2 and relatively low oxygen concentrations
relatively high oxygen and relatively low CO2 concentrations
relatively low CO2 and oxygen concentrations
relatively low oxygen and CO2 concentrations

Answer 27

relatively high CO2 and relatively low oxygen concentrations

Question 28

Which of the following is the most common category of bacteria?

neutrophiles
acidophiles
alkaliphiles
extreme alkaliphiles

Answer 28

neutrophiles

Question 29

Which type of microbes thrive in the Great Salt Lake?

extreme halophiles
barophilic
barotolerant
halotolerant

Answer 29

extreme halophiles

Question 30

Halotolerant microbes cannot grow without high concentrations of salt.

True
False

Answer 30

False

Question 31

Human pathogens are generally which type of microbe?

mesophiles
psychrophiles
psychrotrophs
thermophiles

Answer 31

mesophiles

Question 32

Which best describes bacterial growth during the log phase of the growth curve?

exponential
linear
stationary
S-shaped

Answer 32

exponential

Question 33

MacConkey agar can be used to select for the growth of gram-positive bacteria, making it especially useful to study Enterobacteriaceae.

True
False

Answer 33

False

Question 34

Food spoilage is often caused by which type of microbe?

psychrotrophs
mesophiles
psychrophiles
thermophiles

Answer 34

psychrotrophs

Question 35

Which of the following is the correct order of phases of growth in the growth curve of a batch culture?

lag phase, log phase, stationary phase, death/decline phase
death/decline phase, lag phase, log phase, stationary phase
log phase, lag phase, stationary phase, death/decline phase
statioary phase, log phase, lag phase, death/decline phase

Answer 35

lag phase, log phase, stationary phase, death/decline phase

Question 36

A candle jar is often used to grow which type of bacteria?

capnophiles
microaerophiles
obligate aerobes
obligate anaerobes

Answer 36

capnophiles