Chapter 4: Microbial Growth and Its Control Flashcards

1
Q

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 ___________

A

microaerophile

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2
Q

What is true of the cardinal temperatures?

A

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

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3
Q

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

A

It cannot grow, although it may survive.

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4
Q

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

A

hyperthermophile

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5
Q

Most organisms that live in aerobic environments require catalase and __________

A

superoxide dismutase

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6
Q

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 ________

A

defined medium

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7
Q

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?

A

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

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8
Q

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

A

Sulfur (S)

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9
Q

Why do facultative anaerobes grow better when oxygen is present?

A

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

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10
Q

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

A

No, because organic material may protect microbes from exposure.

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11
Q

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 ___________

A

microaerophile

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12
Q

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?

A

no, because it is likely that a biofilm has formed

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13
Q

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

A

Microbes are sensitive to pH.

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14
Q

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?

A

It is classified in domain Archaea

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15
Q

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

A

Access to nutrients may vary by location

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16
Q

Human pathogens are generally _______

A

mesophiles

17
Q

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

A

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

18
Q

Microbes that can survive in extremely dry environments are called ______

A

xerophiles

19
Q

The term for eliminating or killing all microbes present is _______

A

sterilization

20
Q

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

A

using an autoclave

21
Q

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?

A

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.

22
Q

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

A

acidophile