Deck 5: Environmental Influences and Control of Microbial Growth

Question 1

Human pathogens are:

A) halophiles
B) psychrophiles
C) mesophiles
D) thermophiles
E) extreme thermophiles

Answer 1

C

Question 2

Many __________ have been isolated from the ocean floor environment.

A) psychrophiles
B) mesophiles
C) thermophiles
D) barophiles
E) acidophiles

Answer 2

D

Question 3

The pressure (psi-pounds per square inch) at Earth's surface is:

A) 0 psi
B) 3 psi
C) 5 psi
D) 7 psi
E) 14 psi

Answer 3

E

Question 4

Which temperature is quickly lethal to any mesophile?

A) its optimum growth temperature
B) its minimum growth temperature
C) its maximum growth temperature
D) refrigeration temperature
E) autoclave temperature

Question 5

Which pair of traits can the same organism have?

A) obligate aerobe; obligate anaerobe
B) Gram-positive; Gram-negative
C) thermophile; facultative anaerobe
D) obligate anaerobe; catalase producer
E) microaerophile; grows in 21% oxygen

Question 6

Organisms adapted to grow at overwhelmingly high pressures are called __________.

A) psychrophiles
B) thermophiles
C) barophiles
D) acidophiles
E) mesophiles

Question 7

Which of the following is NOT true about thermophiles?

A) Their proteins contain less glycine.
B) They have more unsaturated linear lipids in their membranes.
C) They have chaperone proteins.
D) Their genomes are packed with numerous DNA-binding proteins that stabilize DNA.
E) They have special enzymes that function to tightly coil DNA.

Question 8

Psychrophiles favor the cold since their membranes are more fluid at low temperature owing to the high proportion of __________ present.

A) saturated fatty acids
B) unsaturated fatty acids
C) lipopolysaccharides
D) transport proteins
E) water

Question 9

Piezophile is another term for __________.

A) acidophile
B) halophile
C) psychrophile
D) baroltolerant
E) barophile

Question 10

Which of the following are used to assess which genes are expressed to make RNA in a given organism at a given time or under a given condition?

A) DNA microarrays
B) PCR
C) DNA sequencing
D) fluorescence microscopy
E) viable cell counts

Question 11

Most bacteria require water activity to be greater than:

A) 0.10
B) 0.25
C) 0.74
D) 0.98
E) 1.0

Question 12

__________ are prominent flora beneath icebergs in the Arctic and Antarctic.

A) Barophiles
B) Psychrophiles
C) Mesophiles
D) Thermophiles
E) Acidophiles

Question 13

All of the following are true about microbes and temperature EXCEPT:

A) Microbes have mechanisms to control their temperature.
B) Temperature affects the average rate of molecular motion.
C) Changes in temperature affect membrane fluidity.
D) Changes in temperature affect transport.
E) Every organism has an optimum temperature for growth.

Question 14

At the bottom of the ocean, hydrostatic pressure averages a crushing 400 atm (atmospheres) and can go as high as:

A) 700 atm
B) 1,000 atm
C) 1,500 atm
D) 3,000 atm
E) 3,500 atm

Question 15

The membrane needs to remain __________ so that it can expand as cells grow larger and so that proteins needed for solute transport can be inserted into the membrane.

A) rigid
B) warm
C) fluid
D) hypertonic
E) polarized

Question 16

The general result of the Arrhenius equation is that growth rate roughly doubles for every __________°C rise in temperature.

A) 5
B) 10
C) 15
D) 20
E) 25

Question 17

The fastest growth rate for a species occurs at temperatures where a cell's __________ work most efficiently.

A) lipids
B) membranes
C) nucleic acids
D) proteins
E) polysaccharides

Question 18

__________ enzymes are stable in part because they contain relatively low amounts of the amino acid glycine.

A) Psychrophilic
B) Acidophilic
C) Thermophilic
D) Halophilic
E) Barophilic

Question 19

__________ typically evolve to survive multiple extreme environments.

A) Psychrophiles
B) Extremophiles
C) Halophiles
D) Thermophiles
E) Acidophiles

Question 20

__________ grow at temperatures as high as 110°C, which occur under extreme pressure.

A) Thermophiles
B) Extreme halophiles
C) Psychrophiles
D) Hyperpsychrophiles
E) Hyperthermophiles

Question 21

During the starvation response, most organisms can do all of the following EXCEPT:

A) retool transport systems for the uptake of different nutrients
B) form metabolically inactive endospores
C) protect against reactive oxygen species
D) protect against temperature extremes
E) protect against pH extremes

Question 22

An organism which requires full oxygen tensions of 21% for growth is:

A) aerobic
B) microaerophilic
C) aerotolerant
D) anaerobic
E) facultative

Question 23

Which of the following is true of microbes and their membranes?

A) They are relatively permeable to protons.
B) Protons can leak through directly when the difference in intracellular and extracellular pH is very high.
C) Membrane-permeant organic acids can prevent the leakage of protons.
D) They are able to change the pH optima of their enzymes.
E) Acidophiles use Na⁺/H⁺ antiporters to remove internal protons.

Question 24

Microbes accumulate __________ in the cell to prevent cell water loss in a hypertonic environment.

A) water
B) proteins
C) sugars
D) acids
E) compatible solutes

Question 25

Which of the following is NOT true of proton motive force in bacteria?

A) It is used in the generation of energy in the form of ADP.
B) It is used to turn the flagellar motor.
C) It can be used for nutrient transport.
D) It produces a transmembrane electrochemical gradient.
E) All of the above are true.

Question 26

Which best describes microaerophiles?

A) They require atmospheric oxygen levels to grow.
B) They cannot grow in the presence of oxygen.
C) They will use oxygen if it is present, but can grow even if oxygen is not present.
D) They require a small amount of oxygen.
E) They can't use oxygen to grow, but oxygen won't kill them.

Question 27

Special channels for helping water move across the membrane quickly are called:

A) compatible solutes
B) osmolarity
C) aquaporins
D) mechanosensitive channels
E) chaperones

Question 28

Many __________ bacteria cause horrific human diseases, such as tetanus, botulism, and gangrene.

A) aerobic
B) anaerobic
C) psychrophilic
D) halophilic
E) fermentative

Question 29

Runoff from agricultural fields, lawns, and golf courses can cause an overgrowth of microbes due to:

A) eutrophication
B) starvation response
C) oligotrophy
D) antisepsis
E) pasteurization

Question 30

An organism that grows at the top of a tube of thioglycolate broth medium is probably a(n):

A) obligate aerobe
B) facultative anaerobe
C) aerotolerant anaerobe
D) microaerophile
E) obligate anaerobe

Question 31

The use of oxygen as the terminal electron acceptor is called __________.

A) aerobic respiration
B) anaerobic respiration
C) fermentation
D) oxygenic photosynthesis
E) carbon dioxide fixation

Question 32

__________ are often chemoautotrophs that oxidize reduced metals and generate strong acids such as sulfuric acid.

A) Acidophiles
B) Psychrophiles
C) Halophiles
D) Mesophiles
E) Barophiles

Question 33

__________ are commonly used to control microbial growth in foods.

A) Weak acids
B) Strong acids
C) Weak bases
D) Strong bases
E) Enzymes

Question 34

A bacterium that thrives in your stomach is probably a/an:

A) thermophile
B) neutrophile
C) alkalophile
D) acidophile
E) psychrophile

Question 35

An organism that grows at the bottom of a tube of thioglycolate broth medium is probably a(n):

A) obligate aerobe
B) facultative anaerobe
C) aerotolerant anaerobe
D) microaerophile
E) obligate anaerobe

Question 36

The proteins and cell components of halophiles require remarkably high intracellular levels of what to maintain their structure?

A) Ca⁺⁺
B) H⁺
C) K⁺
D) Na⁺
E) S

Question 37

A __________ medium is one of higher osmolarity than the cell.

A) hypertonic
B) hypotonic
C) isotonic
D) defined
E) complex

Question 38

E. coli tolerates a pH range of 2-9, which is a what-fold difference in hydrogen ion concentration?

A) 7-fold
B) 100-fold
C) 1,000-fold
D) 10,000-fold
E) 10,000,000-fold

Question 39

__________ is a measure of the number of solute molecules in solution and is inversely related to water activity.

A) Osmolarity
B) Hypertonic
C) Hypotonic
D) Isotonic
E) D-value

Question 40

Which category best describes E. coli?

A) strict aerobe
B) aerotolerant anaerobe
C) facultative aerobe
D) microaerophile
E) strict anaerobe

Question 41

The D-value of a bacterial culture heated to 100°C is the time it takes to kill __________% of the population.

A) 99
B) 90
C) 50
D) 10
E) 1

Question 42

Halophiles actually require high salt concentrations to survive. Describe a mechanism involving compatible solutes that has evolved to achieve low internal sodium ion concentrations.

Question 43

Describe three mechanisms organisms use to reduce osmotic stress.

Question 44

What is a neutralophile? Neutralophiles were once referred to as neutrophiles. Why is this no longer the case?

Question 45

How are some organisms able to survive temporary exposures to elevated temperatures?

Question 46

Which if the following uses microbes to detoxify environmental contaminants?

A) PCR
B) DNA microarrays
C) DNA sequencing
D) antibioisis
E) bioremediation

Question 47

The type of antimicrobial drug that would be least toxic to humans is a drug that:

A) inhibits protein synthesis
B) disrupts the cytoplasmic membrane
C) inhibits nucleic acid synthesis
D) inhibits metabolic pathways
E) inhibits cell wall synthesis

Question 48

Which of the following is NOT true concerning irradiation of foods?

A) Food consumed by NASA astronauts is sterilized by irradiation.
B) Foods become radioactive when irradiated.
C) Viruses are resistant to doses approved for foods.
D) A higher dose of radiation is necessary to kill microbes in frozen foods.
E) It is effective in eliminating parasites and bacteria.

Question 49

How does pH affect proteins? Why do proteins have an optimum, minimum, and maximum pH at which they will function?

Question 50

Disposable plasticware such as petri dishes can be sterilized using which of the following?

A) ethylene oxide
B) steam autoclave
C) low temperature/longtime pasteurization
D) phenol
E) 70% ethanol

Question 51

The conditions used in an autoclave may be reproduced at home in:

A) a rice cooker
B) a double-boiler
C) a microwave
D) a pressure cooker
E) boiling water

Question 52

The D- and z-values are used to adjust conditions for sterilization:

A) at a higher temperature
B) at a lower temperature
C) at a higher pressure
D) at a lower pressure
E) for a shorter period of time

Question 53

Briefly compare how DNA microarrays and two-dimensional protein gels are used to study the response of organisms to environmental stresses.

Question 54

A virus that kills bacteria is called a:

A) bacteriophage
B) viroid
C) spore
D) probiotic
E) porin

Question 55

The dairy creamer used in restaurants is usually sterilized by:

A) filtration
B) ionizing radiation
C) UHT sterilization
D) autoclaving
E) pasteurization

Question 56

Give an example of a naturally occurring organic acid stress situation in the food industry. How does the food industry mimic this, and why?

Question 57

Why are many barophiles also psychrophiles and how are the adaptations for barophiles and psychrophiles similar?

Question 58

No one ever expected to find microbes thriving in our stomachs. What organism was found there, what problem does it cause, and how does it survive there?

Question 59

Which of the following typically will survive autoclaving under standard laboratory operating conditions?

A) mesophile
B) thermophile
C) endospore former
D) Mycobacterium tuberculosis
E) none of the above

Question 60

Why are thermophiles able to survive at temperatures that would quickly kill most mesophiles? Describe at least three adaptations.

Question 61

Why is oxygen so dangerous for cells and how do cells deal with these problems?

Question 62

What alkaliphile do pink flamingos eat and how is it involved in making the flamingo pink?

Question 63

Why do some microorganisms produce antibiotics and how do they avoid being harmed by the antibiotics they produce?

Question 64

Some oligotrophs are actually poisoned by concentrated organics or commit suicide in rich media, therefore actually requiring low nutrient levels to survive. What are prothecae, and what do they accomplish for an oligotroph?

Question 65

Why is death a logarithmic function and NOT an instantaneous event upon treatment?

Question 66

Describe the studies with Salmonella that showed that in vitro conditions do not always model what happens in vivo (in this case in the phagocytic vacuole).

Question 67

Why is moist heat more efficient at killing microbes than dry heat? How does an autoclave kill microbes so efficiently?

Question 68

How is the phenol coefficient calculated? Why is phenol the standard for testing other disinfectants?

Question 69

What is biocontrol? Describe two examples.

Question 70

Briefly describe three techniques used to culture anaerobes in the laboratory.