Chapter 4: Microbial Growth and Its Control

Question 1

A microbial sample is unable to grow in a normal batch culture but does not grow in an anaerobic environment either. This organism is a ___________

Answer 1

microaerophile

Question 2

What is true of the cardinal temperatures?

Answer 2

The optimal temperature is closer to the maximum temperature than the minimum temperature.

Question 3

What happens if an obligate anaerobe such as Clostridium is exposed to air?

Answer 3

It cannot grow, although it may survive.

Question 4

A microbe that lives in a hydrothermal vent at 109 degrees celsius is a _________

Answer 4

hyperthermophile

Question 5

Most organisms that live in aerobic environments require catalase and __________

Answer 5

superoxide dismutase

Question 6

A researcher carefully combines 10 grams of glucose, 8 grams of buffer components and 4 grams each of six specific nutrients before adding them to 900 ml of distilled water. This medium is best described as a ________

Answer 6

defined medium

Question 7

A researcher realizes that the cytoplasm of a microbe has a pH of 6.0. Knowing that a microbe is an acidophile, she injects acid into the cytoplasm to lower the pH to 4.0. What do you predict will happen?

Answer 7

THe microbe will probably die because its internal pH is too low

Question 8

What is one of the major elements that is required by cells, making up most of their dry weight?

Answer 8

Sulfur (S)

Question 9

Why do facultative anaerobes grow better when oxygen is present?

Answer 9

They can use aerobic respiration, which produces more adenosine triphosphate (ATP) than fermentation or anaerobic respiration

Question 10

Do disinfectants work the same when used in standard, real-world situations as they do in the laboratory?

Answer 10

No, because organic material may protect microbes from exposure.

Question 11

A thioglycolate broth culture that contains a thin band without growth, a thin band with growth, and then a large region without growth that extends to the bottom of the tube contains an ___________

Answer 11

microaerophile

Question 12

a test tube of bacteria is allowed to sit undisturbed in the lab for an extended time , and then the growth is estimated using turbidity measurements. Do you predict that this estimate will be accurate?

Answer 12

no, because it is likely that a biofilm has formed

Question 13

Why do defined culture media often contain the components of a buffer, such as K2HPO4 and KH2PO4?

Answer 13

Microbes are sensitive to pH.

Question 14

A researcher obtains a microbe from a very hot environment with an average temperature of about 101 degrees Celsius. What can he be most confident is true?

Answer 14

It is classified in domain Archaea

Question 15

What is one way in which microbes in a biofilm may differ based on their location?

Answer 15

Access to nutrients may vary by location

Question 16

Human pathogens are generally _______

Answer 16

mesophiles

Question 17

A bacterial culture has accidentally been left for more than a year in the back of an incubator. Is it sterile?

Answer 17

No, because a few bacteria may have survived even though it is in the decline phase.

Question 18

Microbes that can survive in extremely dry environments are called ______

Answer 18

xerophiles

Question 19

The term for eliminating or killing all microbes present is _______

Answer 19

sterilization

Question 20

One of the most common methods for sterilization, which uses moist heat, is _________

Answer 20

using an autoclave

Question 21

If you transfer an old culture of bacteria to a new experimental medium with a very distinctive composition, when should you take a sample if you want to study them during the exponential growth phase?

Answer 21

You should leave the bacteria a little longer than usual before sampling as the lag phase will be long due to the unusual medium and the age of the culture.

Question 22

An organism that thrives at a pH of 2 is called an _______

Answer 22

acidophile