Deck 6: Microbial Nutrition and Growth

Question 1

Which of the following forms of oxygen is detoxified by the enzyme catalase?

A) singlet oxygen
B) hydroxyl radical
C) peroxide anion
D) superoxide radical
E) molecular oxygen

Answer 1

C

Question 2

An epidemiologist is investigating a new disease and observes what appear to be bacteria inside tissue cells in clinical samples from victims. The scientist wants to try to isolate the bacteria in the lab. What culture conditions are most likely to be successful?

A) culturing on blood agar plates
B) inoculation of EMB plates
C) incubation in a candle jar
D) inoculation of cell cultures
E) inoculation of a minimal medium broth

Answer 2

D

Question 3

A microbiologist inoculates a growth medium with 100 bacterial cells/ml. If the generation time of the species is 1 hour, and there is no lag phase, how long will it be before the culture contains more than 10,000 cells/ml?

A) 24 hours
B) 7 hours
C) 2 hours
D) 3 hours
E) 10 hours

Answer 3

B

Question 4

Obligate anaerobes may be cultured in the laboratory

A) in a reducing medium.
B) in a candle jar.
C) in standard Petri plates.
D) on blood agar plates.
E) on blood agar plates in a candle jar.

Question 5

A microbe that grows only at the bottom of a tube of thioglycollate medium is probably a(n)

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

Question 6

All of the following are used to protect organisms from the toxic by-products of oxygen EXCEPT

A) carotenoids.
B) superoxide dismutase.
C) peroxidase.
D) protease.
E) catalase.

Question 7

Which of the following organisms would be most likely to contaminate a jar of pickles?

A) a neutrophile
B) a thermophile
C) an acidophile
D) an obligate anaerobe
E) a mesophile

Question 8

An aquatic microbe that can grow only at the surface of the water is probably which of the following?

A) a phototroph
B) a heterotroph
C) a chemotroph
D) a lithotroph
E) an anaerobe

Question 9

In microbiology, the term growth usually refers to an increase in

A) a microbe's size.
B) the number of microbial cells.
C) the amount of ATP produced.
D) the number and size of microbial cells.
E) the number and size of microbial cells and the amount of ATP produced.

Question 10

Human pathogens are classified as

A) thermoduric.
B) thermophiles.
C) mesophiles.
D) hyperthermophiles.
E) psychrophiles.

Question 11

Joan wants to discover a microbe capable of degrading an environmental contaminant. Which of the following refers to the process she should use?

A) cell culture
B) chemostat
C) quorum sensing
D) enrichment culture
E) nitrogen fixation

Question 12

A fastidious organism might be grown on which of the following types of media?

A) transport media
B) reducing media
C) enriched media
D) differential media
E) selective media

Question 13

The term barophile refers to which of the following growth requirements?

A) hydrostatic pressure
B) temperature
C) nitrogen source
D) pH
E) osmotic pressure

Question 14

At temperatures higher than the maximum growth temperature for an organism,

A) proteins are permanently denatured.
B) membranes become too fluid for proper function.
C) hydrogen bonds within molecules are broken.
D) hydrogen bonds are broken, and proteins are permanently denatured.
E) hydrogen bonds are broken, proteins are denatured, and membranes become too fluid.

Question 15

Organisms that can grow with or without oxygen present are

A) obligate aerobes.
B) facultative anaerobes.
C) aerotolerant anaerobes.
D) obligate anaerobes.
E) either facultative anaerobes or aerotolerant anaerobes.

Question 16

A(n) __________ organism is one that requires oxygen for growth.

A) anaerobic
B) facultative anaerobic
C) aerotolerant
D) obligate aerobic
E) both aerotolerant and anaerobic

Question 17

Which of the following growth factors would NOT be required by microbes which do not utilize electron transport chains?

A) heme.
B) selenium.
C) NADH.
D) vitamins.
E) amino acids.

Question 18

Nitrogen is a growth limiting nutrient for many organisms because

A) it is necessary for the biosynthesis of amino acids.
B) it is required for synthesis of nucleotides.
C) it is required for lipid synthesis.
D) only a small number of bacteria are able to extract it from the atmosphere.
E) only a few microbes can extract it from the atmosphere, but all organisms require it for amino acid and nucleotide synthesis.

Question 19

A cell that uses an organic carbon source and obtains energy from light would be called a

A) photoheterotroph.
B) lithoautotroph.
C) photoautotroph.
D) chemoheterotroph.
E) chemoautotroph.

Question 20

Which of the following measurement techniques would be useful to quantify a species of bacteria that is difficult to culture?

A) membrane filtration
B) viable plate counts
C) MPN
D) microscopic counts
E) metabolic activity

Question 21

During which growth phase are bacteria more susceptible to antimicrobial drugs?

A) lag phase
B) log phase
C) stationary phase
D) death phase
E) the susceptibility is the same for all phases

Question 22

Which of the following is NOT a direct method for measuring the number of microbes in a sample?

A) viable plate counts
B) turbidity
C) Coulter counter
D) MPN
E) membrane filtration

Question 23

The use of salt and sugar in preserving various types of foods is an application of which of the following concepts?

A) nitrogen fixation
B) osmotic pressure
C) pH
D) hydrostatic pressure
E) quorum sensing

Question 24

Cells are rapidly growing and dividing during the __________ of growth.

A) death phase
B) lag phase
C) log phase
D) stationary phase
E) indeterminate phase

Question 25

Which of the following quantification techniques can distinguish living cells from dead cells in a culture?

A) microscopic counts
B) dry weight
C) metabolic activity
D) a Coulter counter
E) turbidity

Question 26

__________ are complex communities of various types of microbes that adhere to surfaces.

A) Aggregates
B) Colonies
C) Isolates
D) Biofilms
E) Media

Question 27

Another term for the logarithmic growth of bacterial cells is

A) generation time.
B) exponential growth.
C) arithmetic growth.
D) absorbance.
E) binary fission.

Question 28

Metabolic activity is at maximum level in the __________ of growth.

A) lag phase
B) log phase
C) death phase
D) stationary phase
E) intermediate phase

Question 29

A clinical sample labeled as "sputum" was collected from

A) the skin.
B) the blood.
C) the central nervous system.
D) a piece of tissue.
E) the lungs.

Question 30

When cells are metabolically active but not dividing, they are in the

A) stationary phase.
B) log phase.
C) lag phase.
D) death phase.
E) exponential phase.

Question 31

Sodium thioglycollate is associated with which of the following types of media?

A) transport media
B) differential media
C) complex media
D) reducing media
E) selective media

Question 32

during the __________ of growth, new cells are being produced at the same rate as other cells are dying.

A) lag phase
B) log phase
C) death phase
D) stationary phase
E) intermediate phase

Question 33

A Petroff-Hauser counting chamber is

A) a glass slide containing an etched grid for counting microbes directly using a microscope.
B) a device that counts cells as they interrupt an electrical current.
C) a device that measures the amount of light that passes through a culture.
D) an apparatus that traps bacterial cells on a membrane filter where they can be counted.
E) a device used to count numbers of bacterial colonies on a Petri plate.

Question 34

MacConkey agar plates represent __________ medium.

A) a minimal
B) a selective
C) a differential
D) both a differential and a selective
E) both a minimal and a selective

Question 35

During the __________ of growth, cells are dying faster than new cells are being produced.

A) death phase
B) lag phase
C) log phase
D) stationary phase
E) longitudinal phase

Question 36

A colony-forming unit is the number of cells

A) in a colony.
B) that produces one colony.
C) in a particular specimen.
D) that is in exponential phase in a culture.
E) that can be placed on a Petri plate.

Question 37

All of the following ingredients might be found in complex media EXCEPT

A) hydrogen peroxide.
B) yeast extract.
C) blood.
D) soy extract.
E) milk proteins.

Question 38

A specimen of urine is determined to contain 30 bacterial cells per microliter. How many cells would be present in a milliliter?

A) 3
B) 300
C) 30,000
D) 3,000
E) 30 million

Question 39

A device that removes wastes and adds fresh medium to bacterial cultures in order to prolong the log phase of a culture is called a(n)

A) Coulter counter.
B) cytometer.
C) spectrophotometer.
D) pellicle.
E) chemostat.

Question 40

The method of obtaining isolated cultures that utilizes surface area to dilute specimens is called

A) the pour-plate technique.
B) serial dilution.
C) the streak-plate technique.
D) transport media.
E) enrichment culturing.

Question 41

A microorganism found living under conditions of high __________ is a barophile.

A) pH values
B) oxygen concentrations
C) hydrostatic pressure
D) carbon dioxide levels
E) salt concentrations

Question 42

The __________ growth temperature is the temperature at which an organism exhibits the highest growth rate.

Question 43

Organisms that require organic sources of carbon and energy are called __________.

Question 44

A capnophile is a microorganism that thrives in conditions of high __________.

A) carbon dioxide levels
B) hydrostatic pressure
C) oxygen levels
D) pH
E) salt concentration

Question 45

Quorum sensing is a process by which bacteria respond to the density of other bacteria in their environment.

Question 46

Microaerophiles are microbes that grow best at low

A) carbon dioxide levels.
B) pH values.
C) hydrostatic pressure.
D) oxygen levels.
E) salt concentrations.

Question 47

Nitrogen fixation is a process that occurs in all bacteria.

Question 48

Obligate anaerobes have enzymes such as superoxide dismutase to protect them from the damaging effects of oxygen.

Question 49

An obligate anaerobe can be cultured in a candle jar.

Question 50

The __________ radical is formed during the incomplete reduction of O₂ during electron transport in aerobes.

Question 51

The only effective way to store bacterial cultures for short periods of time is to arrest their metabolism by freezing.

Question 52

Thermoduric mesophiles are often responsible for spoilage of improperly canned foods.

Question 53

A selective medium can be formulated either by including inhibitory chemical substances or by leaving out a single crucial nutrient.

Question 54

An organism that tolerates high __________ is called a halophile.

A) hydrostatic pressure
B) salt concentrations
C) pH
D) carbon dioxide levels
E) oxygen levels

Question 55

Agar is a useful compound in the microbiology lab because it is an excellent nutrient for bacteria.

Question 56

Bacteria that thrive at human body temperatures are classified as __________.

Question 57

An acidophile thrives under conditions of low

A) carbon dioxide levels.
B) salt concentrations.
C) oxygen levels.
D) hydrostatic pressure.
E) pH.

Question 58

The conversion of nitrogen gas to ammonia is called nitrogen __________.

Question 59

In spectrophotometry, 40% light transmission is the same thing as 60% absorbance of light.

Question 60

An obligate halophile will burst if placed in freshwater.

Question 61

A(n) __________ can measure changes in the turbidity of a bacterial culture.

Question 62

A film of cells at the surface of a broth is called a(n) __________.

Question 63

A sample placed into fresh medium is typically initially in the __________ phase of microbial growth.

Question 64

Compare and contrast the streak-plate method of isolation with the pour-plate method of isolation.

Question 65

A gelling agent derived from algae that is useful for creating solid growth media is called __________.

Question 66

Explain how temperature and pH levels can influence microbial infections in the human body.

Question 67

A pure culture is composed of cells that arise from a single __________.

Question 68

Flow __________ is a method of counting cells that have been stained or tagged with fluorescent dyes.

Question 69

A growth curve plots the __________ of organisms in a growing population over time.

Question 70

Cells that are exposed to hypertonic environments will exhibit __________.

Question 71

Alkalinophiles can survive in water up to pH __________. (Be sure your answer is a numeral.)

Question 72

A(n) __________ is a sample of microorganisms introduced into a growth medium.

Question 73

Explain how aerobic organisms tolerate the presence of oxygen in their metabolic pathways despite its toxic properties.

Question 74

Genetic methods of detecting microorganisms reveal that the number of bacterial species in nature exceeds previous estimates by several orders of magnitude. In the human mouth, for example, it is estimated that 500-700 microbial species are normally present. Explain why previous estimates were low.

Question 75

Explain the similarities and differences between direct and indirect methods of measuring microbial growth, and give examples of each.