Chapter 6

Question 1

Bacteria that CANNOT grow in the presence of oxygen (O2) are called __________.

Answer 1

obligate anaerobes

Question 2

used to preserve bacterial cultures

Answer 2

lyophilization (freeze-drying)
freezing quickly and storing at –70°C
refrigeration

Question 3

During log phase, bacteria are __________.

Answer 3

dividing at the fastest possible rate

Question 4

Bacteria reproduce by __________.

Answer 4

binary fission

Question 5

Bacteria that spoil food in the refrigerator are most likely __________.

Answer 5

psychrotrophs

Question 6

Which of the following statements regarding biofilms is true?

Answer 6

The microbes in biofilms can work cooperatively to carry out complex tasks.

Question 7

culture media are accurate

Answer 7

Chemically defined medium is specifically formulated, and each ingredient’s exact composition is known.
Complex media are formulated from nutrient-rich whole food sources whose exact ingredients may not be known.
Reducing media are complex media containing chemicals, such as thioglycolate, that combine with oxygen, creating an anaerobic environment.

Question 8

A medium containing chemicals to inhibit the growth of gram-positive bacteria would be called __________.

Answer 8

Selective

Question 9

Which level of biosafety (BSL) is appropriate for handling organisms that present the highest risk level for infection and the lowest success rate for prevention and treatment?

Answer 9

BSL-4

Question 10

If a single bacterium replicated every 30 minutes, how many bacteria would be present in 2 hours?

Answer 10

16

Question 11

In which phase of the growth curve is the population-doubling time fastest?

Answer 11

Log phase

Question 12

During the lag phase, __________.

Answer 12

cells are engaged in intense enzymatic activity

Question 13

method used for the direct measurement of microbial growth

Answer 13

spread plates
the most probable number (MPN) method
filtration
serial dilutions

Question 14

An organism displays some growth at 4°C and at 25°C. However, it grows best at 20°C. This organism would be classified as a __________.

Answer 14

psychrotroph

Question 15

The ability of microbes to utilize N2 as a nitrogen source is called __________.

Answer 15

nitrogen fixation

Question 16

Through metabolism, pathogens often produce acids that interfere with their own growth. __________ are/is added to media to control pH changes.

Answer 16

Buffer

Question 17

extreme halophiles

Answer 17

30% salt

Question 18

acidophiles

Answer 18

low pH

Question 19

psychrophiles

Answer 19

0°C

Question 20

When a bacterial cell reproduces by splitting into two daughter cells, the process is called __________.

Answer 20

Binary fission

Question 21

An organism that grows both in the presence and the absence of oxygen and uses oxygen when it is available is called a/an __________.

Answer 21

facultative anaerobe

Question 22

Microaerophiles do NOT require oxygen for growth.

Answer 22

False

Question 23

Most bacteria grow best at pH

Answer 23

7

Question 24

Psychrotroph

Answer 24

growth at 0°C

Question 25

Mesophile

Answer 25

growth at 25°C

Question 26

Psychrophile

Answer 26

growth at 15°C

Question 27

Hyperthermophiles

Answer 27

growth at 100°C

Question 28

Which of the following is the best definition of generation time?

Answer 28

The length of time needed for a cell to divide

Question 29

Patients with indwelling catheters are susceptible to infections because

Answer 29

Biofilms develop on catheters.

Question 30

Which of the following is an example of a metabolic activity that could be used to measure microbial growth?

Answer 30

Glucose consumption