mcb ch 6

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0°C

A psychrophile grows best at

Extreme halophiles

Organisms that require very high salt concentrations for growth are called

Sulfur

he energy source utilized by producers in the hydrothermal vents on the ocean floor is

Nitrogen fixation

Some microorganisms use gaseous nitrogen directly from the atmosphere in a process called

Facultative aerobe

An organism that uses oxygen but can grow without oxygen is called a(n)

Obligate anaerobe

This organism is killed by atmospheric oxygen:

Reducing media

To cultivate anaerobic bacteria, one must use special media called

Carbon dioxide

Capnophiles must be grown in high concentrations of

Enrichment

The culture medium that is designed to increase numbers of
desired microbes to detectable levels is called

Selective

The culture medium that is designed to suppress unwanted microbes
while encouraging desired microbes is called

Turbidity

A spectrophotometer can be used to measure

Buffers

The addition of which of the following to a culture medium will neutralize acids? Buffers, Sugars,pH . Heat , Carbon

Hypertonic environment.

Salts and sugars work to preserve foods by creating a

Uses oxygen or but can grow without oxygen.

The term facultative anaerobe refers to an organism that

Counts only live cells.

Which of the following is an advantage of the standard culture plate count?

Does not require an incubation time

Which of the following is an advantage of the direct microscopic count?

Which of the following is not used to determine metabolic activity?

Which of the following is not used to determine metabolic activity?

36

Thirty-six colonies grew in nutrient agar from 1.0 ml of undiluted sample in
a standard plate count. How many bacterial cells were in the original sample?

7.

Most bacteria grow best at pH

Selective medium and Differential medium.

A culture medium on which only gram-positive organisms grow and
a yellow halo surrounds Staphylococcus aureus colonies is called a(n)

Differential medium.

A culture medium consisting of agar, human blood, and beef extract is a

Peptone and beef extract.

The source of nutrients in nutrient agar is

5

An experiment began with 4 cells and ended with 128 cells.
How many generations did the cells go through?

B) Thermophiles can  grow at 37°C

Which of the following pairs is mismatched?
A) Psychrotrophs can  grow at 20°C
b ) Thermophiles can  grow at 37°C
C) Mesophiles can  grow at 25°C
D) Psychrophiles can  grow at 0°C
E) None of the above

Log phase

During which growth phase will gram-positive bacteria be most susceptible to penicillin?

D) Metabolic activity.

All of the following are direct methods to measure microbial growth except
A) Direct microscopic count.
B) Standard plate count.
C) Filtration.
D) Metabolic activity.
E) MPN

Facultative Halophiles

Which group of microorganisms is most likely to spoil a freshwater trout
preserved with salt?

NAD+

Which of the following is an organic growth factor derived from a B vitamin
necessary for the bacterial metabolism?

Glucose consumption

Which of the following metabolic activities can be used to measure microbial growth?

3 × 210

Three cells with generation times of 30 minutes are inoculated into a culture medium.
How many cells are there after 5 hours?

aerotolerant anaerobe.

An organism that has peroxidase and superoxide dismutase but
lacks catalase is most likely an

Obligate anaerobe

Which organism is killed by atmospheric O2?

(NH4)2SO4

Which of the following should not be included in a medium used to select
for a nitrogen-fixing chemoheterotroph?

The same number of cells in both.

Assume you inoculated 100 cells into 100 ml nutrient broth. You then inoculated
100 cells of the same species into 200 ml nutrient broth.
After incubation for 24 hr, you should have

C) consist of only one type of organisms

) All of the following are characteristics of micro-organisms in the Biofilm except
A) exhibit a resistance to antibiotics and disinfectants.
B) can transfer DNA to each other.
C) consist of only one type of organisms
D) communicate with quorum sensing.
E) are a major cause of hospital acquired infections.

Superoxide dismutase

Which enzyme catalyzes the reaction: O2-- + O2-- + 2H+ → H2O2 + O2?

Catalase

Which enzyme catalyzes the reaction: 2 H2O2 → 2 H2O + O2?

Peroxidase

Which enzyme catalyzes the reaction: H2O2 + 2H+ → 2H2O ?

The direct microscope count method

Because of time considerations, which method is usually used
to count the number of bacteria in milk?

Serial dilution

Which method is utilized to ensure that plates containing 25 to 250 colonies
are counted?

Log phase

Microorganisms are particularly sensitive to adverse conditions during the

) 60°C

Which one of the following temperatures would most likely kill a mesophile?

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