Module 4

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Which of these growth curves best describes the growth of Clostridium botulinum (an obligate anaerobe) in the presence of oxygen?
A. a steep incline
B. a slight incline
C. a flat line

C. a flat line

Which of these growth curves best describes the growth of Thoibacillus, an acidophile, at pH 9.0?
A. a steep incline
B. a slight incline
C. a flat line

C. a flat line

For a thermophile, the minimum growth temperature would be ______C.
A. 0
B. 10
C. 37
D. 45

D. 45

Cells that live in high salt environments are called ________.
A. plasmophiles
B. saltophiles
C. tonophiles
D. halophiles

D. halophiles

You want to measure the bacterial number in your used, 10 day old water bottle. Which method would be most effective?
A. direct microscopic count
B. standard plate count
C. filtration
D. metabolic activity

C. filtration

All of the following are true about agar except____.
A. it is a source of nutrients in culture media
B. it is a polysaccharide
C. it solidifies below 40 C.
D. it is used to harden liquids

A. it is a source of nutrients in culture media

While ____ is able to detoxify a reactive oxygen species, it also produces one, hydrogen peroxide.
A. Superoxide dismutase
B. Catalase
C. Peroxidase
D. Oxygenase

A. Superoxide dismutase

Luria Broth (LB) is a medium containing Tryptone, yeast extract, and sodium chloride.
A. LB is a chemically defined medium
B. LB is a complex medium
C. There is not enough information presented
D. Depends if agar is present or not

B. LB is a complex medium

Motility medium is a growth agar medium that contains a low agar concentration. Cells that are motile will be able to grow throughout the medium wheras non-motile cells will only grow where they were inoculated. What type of medium is motility medium?
A. differential
B. Selective
D. Differential and selective
D. Enrichment

A. differential

Which of these does not contain nitrogen?
A. Carbohydrates
B. Proteins

A. Carbohydrates

Most bacterial reproduce by_______.
A. sexual reproduction
B. binary fission
C. budding
D. mitosis

B. binary fission

What toxic oxygen form of oxygen does the enzyme catalase detoxify?
A. superoxide free radical
B. Singlet oxygen
C. Peroxide anion
D. Hydroxyl radical

C. Peroxide anion

Which of these quantification methods would be most accurate when quantifying a filamentous mold culture?
A. plate count
B. filtration
C. turbidity
D. dry weight

D. dry weight

Which of the following organisms most likely does not have catalase?
A. an aerotolerant anaerobe
B. an obligate anaerobe
C. a facultative anaerobe
D. an obligate aerobe

B. an obligate anaerobe

The large intestines is an environment that lacks any oxygen. Which of the following types of organisms would most likely be found there?
A. obligate aerobe
B. obligate anaerobe
C. microaerophile
D. aerotolerant anaerobe

B. obligate anaerobe

You want to quantify a culture of motile bacteria. Which method of quantifying would you use if you needed the most accurate information as soon as possible?
A. Plate count
C. Turbidity
D. Microscopic count
E. Dry weight

C. Turbidity

Penicillin functions by inhibiting the formation of new cell walls. At what stage of bacterial growth is penicillin most effective?
A. Lag
B. Log
C. Stationary
D. Phase

B. Log

Which of these growth curves best describes the growth of a psychrophile at room temperature (25C)?
A. a steep incline
B. a slight incline
C. a flat line

C. a flat line

Acidophiles would be expected to grow best at a pH of ___.
A. 4
B. 7
C. 10

A. 4

What is the difference between peroxidase and catalase?
A. Peroxidase detoxifies hydrogen peroxide, catalase detoxifies hydroxyl radicals.
B. Catalase produces oxygen, peroxidase does not
C. Aerotolerant anaerobe use catalase, facultative anaerobes use peroxidase
D. Obligate aerobes use both peroxidase and catalase

B. Catalase produces oxygen, peroxidase does not.

A culture medium on which only gram-positive organisms grow and a yellow halo surrounds Staphylococcus aureus colonies is called a ____.
A. selective medium
B. differential medium
C. enrichment medium
D. A and B

D. A and B

The "streak plate" method is used to ___.
A. isolate individual bacterial colonies
B. determine the growth rate of bacteria
C. determine the size of bacterial cells
D. inhibit bacterial growth

A. isolate individual bacterial colonies

At what stage of bacterial growth is cell division most rapid?
A. lag
B. log
C. Stationary
D. Death

B. Log

Which of these is a good method of preserving microbial cultures?
A. Lyophilization
B. Heating
C. Salting
D. Picklilng

A. Lyophilization

Which method of quantifying bacterial numbers would be most effective for measuring the numbers of bacterial in drinking water, when you expect the numbers to be relatively low?
A. filtration
B. plate cocunt
C. direct microscopic count
D. turbidity

A. filtration

Mannitol salt agar contains 7.5% salt which only allows the growth of microbes asssociated with the human body, such as staphylococcus species. Furthermore, those that are able to ferment mannitol appear yellow in color. What type of medium is Mannitol salt agar?
A. selective
B. differential
C. selective and differential
D. enrichment

C. selective and differential

The streak plate method produces pure cultures by separating individual bacterial cells from one another by____.
A. dragging them across a solid surface
B. dispersing them in liquid media
C. killing off those cells that are not able to survive in hot agar
D. embedding some cells in the agar so that they are exposed to lower concentrations of oxygen

A. dragging them across a solid surface

____ is used if you want to study obligate anaerobic microbes.
A. enrichment media
B. selective media
C. reducing media
D. differential media

C. reducing media

Most human pathogens are ____.
A. psychrophiles
B. mesophiles
C. thermophiles
D. psychrotrophs

B. mesophiles

After growing for 12 hours, a bacterial culture increases from 2 million to 8 million cells in 2 hours. The generation time at this time is ___.
A.12 hours
B.1 hour
C.2 hours
D.10 hours

B. 1 hour

You have a bacterial culture consisting of 2 cells. Assuming the population is growing exponentially, how many cells will be in the culture after 3 hours of growth if the generation time is 30 minutes?
A.12 cells
B.64 cells
C.128 cells
D.2,000,000 cells

C. 128 cells


Cold loving (grow below 0 C, optimum at 15 C, killed above 20 C)


Low temp loving (grow at 0 C, optimum at 20 C)


Moderate temp loving (optimum between 25 - 40 C)


Heat loving (cannot grow below 45 C)


High heat loving

Chemoheterotrophs get carbon from:

Organic sources outside themselves

Chemoautotrophs, photoautotrophs get carbon from:


When bacteria use nitrogen gas (N2) from the atmosphere, this is called____.

Nitrogen fixation

What type of media does the following:
Encourage growth of desired microbe
Supress growth of undesired microbes
Ideally, only desired microbe will grow

Selective media

What type of media has the following characteristics?
Most microbes grow
Desired microbes look different

Differential media

What type of media has the following characteristics?
Designed to increase overall ratio of desired microbe to undersired microbes

Enrichment culture

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