Deck 5: Environmental Influences and Control of Microbial Growth

Question 1

Piezophile is another term for:

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

Answer 1

E

Question 2

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 300 µM oxygen

Answer 2

C

Question 3

The pressure (psi, or 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

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 5

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 6

Human pathogens are:

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

Question 7

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

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

Question 8

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 9

Many __________ have been isolated from the ocean floor environment.

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

Question 10

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 11

Most bacteria require water activity to be greater than:

A) 0.10
B) 0.25
C) 0.74
D) 0.91
E) 1.0

Question 12

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 13

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 14

__________ grow at temperatures as high as 121°C, which occur under extreme pressure.

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

Question 15

__________ have evolved to survive multiple extreme environments.

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

Question 16

Organisms adapted to grow at overwhelmingly high pressures are called:

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

Question 17

__________ 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 18

Psychrophiles favor the cold since their membranes are more fluid at low temperature as a result of the high proportion of __________ present.

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

Question 19

__________ 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 20

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

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

Question 21

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

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

Question 22

The proteins and cell components of halophiles have remarkably high intracellular levels of _________________, which helps to maintain their cell structure.

A) oxygen
B) potassium
C) calcium
D) sodium
E) hydrogen

Question 23

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 24

Which category best describes E. coli?

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

Question 25

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 26

__________ are commonly used to control microbial growth in foods.

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

Question 27

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

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

Question 28

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 29

A bacterium that thrives in your stomach is probably a(n):

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

Question 30

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

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

Question 31

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

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

Question 32

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

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

Question 33

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 34

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

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

Question 35

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 36

____________________ is one of the important signaling molecules that controls global gene expression during starvation.

A) Cyclic AMP
B) ADP
C) ATP
D) Glucose
E) Water

Question 37

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 38

__________ 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 39

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 40

Alkaliphiles use _________________ in addition to proton motive force to maintain pH.

A) potassium motive force
B) sodium motive force
C) calcium motive force
D) magnesium motive force
E) sulfur motive force

Question 41

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

Question 42

A virus that kills bacteria is called a:

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

Question 43

Which of the following uses microbes to detoxify environmental contaminants?

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

Question 44

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

Question 45

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 46

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

Question 47

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 48

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

Question 49

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 50

Describe three mechanisms organisms use to reduce osmotic stress.

Question 51

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 52

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 53

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

A) ethylene oxide
B) steam autoclave
C) low-temperature, long-time pasteurization
D) phenol
E) 70% ethanol

Question 54

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

Question 55

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

Question 56

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 57

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 58

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 59

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

Question 60

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 61

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

Question 62

If a disinfectant is added to a culture containing 1 x 10⁶ CFU per milliliter and the D-value of the disinfectant is 2 minutes, how many viable cells are left after 4 minutes of exposure?

Question 63

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 64

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

Question 65

What is biocontrol? Describe two examples.

Question 66

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

Question 67

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

Question 68

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

Question 69

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

Question 70

If you have a food sample contaminated with anthrax spores, which sterilization approach would make sure the sample is free of spores without compromising the quality of the food sample-autoclaving or irradiation?