Question 1

Which of the following best describes a mesophile based on its optimum temperature for growth?

Accepted Answer

It grows best at temperatures between 20°C and 45°C.

Question 2

A bacterium isolated from a salt lake grows optimally at 3 M NaCl. Which term best describes this organism?

Accepted Answer

Extreme halophile

Question 3

Which of the following equations correctly describes the calculation for the number of cells after a given number of generations in binary fission?

Accepted Answer

$$N = N_0$ 	imes 2^n$$

Question 4

Which of the following best explains why food should not be left in the 'danger zone' (between 15°C and 50°C) for extended periods?

Accepted Answer

Rapid growth of bacteria and possible toxin production can occur.

Question 5

A microbiologist wants to isolate a pure culture from a mixed sample. Which technique is most appropriate?

Accepted Answer

Streak plate method

Question 6

Which of the following best describes an obligate anaerobe?

Accepted Answer

It is killed by the presence of oxygen.

Question 7

Which of the following is a chemically defined medium for growing Escherichia coli?

Accepted Answer

Medium containing glucose, ammonium phosphate, sodium chloride, magnesium sulfate, potassium phosphate, and water

Question 8

Which of the following best describes the stationary phase of a bacterial growth curve?

Accepted Answer

The rate of cell division equals the rate of cell death.

Question 9

A facultative anaerobe is best described as an organism that:

Accepted Answer

Can grow with or without oxygen but grows better with oxygen.

Question 10

Which of the following is a key difference between a defined (synthetic) medium and a complex medium?

Accepted Answer

Defined medium contains only known, specific chemicals.

Question 11

Which of the following best describes a biofilm?

Accepted Answer

A community of microorganisms attached to a surface and embedded in a self-produced matrix

Question 12

Which isolation technique involves mixing a diluted sample with melted agar and pouring it into a Petri dish?

Accepted Answer

Pour plate method

Question 13

A bacterium that uses inorganic compounds as an energy source and CO$$_2 as a $$carbon source is best classified as a:

Accepted Answer

Chemolithoautotroph

Question 14

Which of the following statements about capnophiles is correct?

Accepted Answer

They require elevated levels of CO$$_2$$ for optimal growth.

Question 15

Which of the following best explains why streak plate technique is used in microbiology?

Accepted Answer

To obtain isolated colonies from a mixed culture

Question 16

A microbiologist is working with an obligate anaerobe. Which piece of equipment is most appropriate for culturing this organism?

Accepted Answer

Anaerobic box or jar

Question 17

Which of the following is a growth factor for bacteria?

Accepted Answer

Amino acids

Question 18

Which phase of the bacterial growth curve is characterized by adaptation to new environmental conditions and little to no cell division?

Accepted Answer

Lag phase

Question 19

A culture medium that contains peptone, beef extract, and agar is best described as:

Accepted Answer

A complex medium

Question 20

Which of the following methods is most appropriate for estimating the number of viable bacteria in a sample?

Accepted Answer

Plate count method

Microbial Growth: Environmental Factors, Nutritional Requirements, and Laboratory Techniques

Study Guide - Practice Questions