Deck 6: Microbial Nutrition and Growth

Question 1

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

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

Answer 1

A

Question 2

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

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

Answer 2

D

Question 3

A microbe recovered from an environmental sample grows on a medium composed of agar and a mix of salts. The agar is not digested during incubation. The growth rate increases in high CO 2 conditions. The organism is likely a(n)

A) heterotroph.
B) chemotroph.
C) halophile.
D) autotroph.
E) The answer cannot be determined from the information provided.

Answer 3

D

Question 4

An organism that requires chemical nutrients which serve as final electron acceptors is a(n)

A) chemotroph.
B) aerobe
C) phototroph.
D) lithotroph.
E) autotroph.

Question 5

An organism that produces catalase enzyme is protected from the harmful effects of

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

Question 6

Prokaryotes living in the ocean around volcanic vents use the volcanic gasses carbon dioxide (CO2) and hydrogen sulfide (H2S) to fuel their metabolism. They are therefore

A) photoautotrophs.
B) chemoheterotrophs.
C) lithoheterotrophs.
D) lithoautotrophs.
E) chemoautotrophs.

Question 7

Which of the following oxidizing agents is sometimes produced during aerobic respiration?

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

Question 8

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

Question 9

Obligate anaerobes may be cultured in the laboratory

A) in standard complex media.
B) in standard Petri plates.
C) in a standard incubator.
D) in a reducing medium.
E) on blood agar plates.

Question 10

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

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

Question 11

The are an important source of nitrogen compounds that can be metabolized by most other organisms.

A) algae
B) higher plants
C) Helicobacter pylori
D) cyanobacteria
E) Lactobacillus

Question 12

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

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

Question 13

A food product is labeled as having antioxidants. It may therefore contain

A) vitamin E.
B) vitamin B2 (riboflavin).
C) vitamin C.
D) amino acids.
E) vitamin C or E, or both.

Question 14

Microbial growth rates are controlled in a chemostat by

A) maintaining a constant temperature.
B) allowing waste products to accumulate.
C) controlling the amount of a limiting nutrient.
D) controlling the amount of available oxygen.
E) promoting biofilm formation.

Question 15

Bacteria living in communities of microbes change the genes they are expressing in response to

A) decreasing oxygen.
B) changes in local temperature.
C) changes in hydrostatic pressure.
D) quorum-sensing molecules.
E) changes in pH.

Question 16

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

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

Question 17

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

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

Question 18

You open a jar that has been in the refrigerator for a couple of weeks and find the contents do not look or smell right. What type of microbe has been growing in your refrigerator?

A) hyperthermophile
B) thermoduric
C) thermophile
D) mesophile
E) psychrophile

Question 19

Organisms that can grow with or without oxygen present are

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

Question 20

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) incubation in an anaerobic culture system
C) inoculation of EMB plates
D) inoculation of a minimal medium broth
E) inoculation of cell cultures

Question 21

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

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

Question 22

Which of the following explains why honey can be stored at room temperature for years without spoiling?

A) hydrostatic pressure
B) osmotic pressure
C) low pH
D) lyophilization
E) anaerobic conditions

Question 23

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

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

Question 24

The correct sequence for the phases indicated by the letters A, B, C and D is

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

Question 25

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

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

Question 26

Creating conditions in the laboratory that promote the growth of some microbes while inhibiting the growth of others is called

A) transport conditions.
B) differential culturing.
C) complex culturing.
D) reducing conditions.
E) selective enrichment culturing.

Question 27

All of the following are part of the process of binary fission EXCEPT

A) DNA replication.
B) septum formation.
C) budding.
D) doubling of cell size.
E) cytoplasmic membrane production.

Question 28

Sodium thioglycollate is found in which of the following types of media?

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

Question 29

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

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

Question 30

Students in a microbiology lab are provided plates of medium to use in their bacterial culturing. The growth of organisms that can metabolize mannose sugar will result in the agar turning yellow, while the agar color remains unchanged if the mannose is not metabolized. The plates contain a medium.

A) reducing
B) transport
C) differential
D) defined
E) selective

Question 31

Which of the following is an approach to preventing the formation of biofilms?

A) blocking the activity of carbohydrate catabolism
B) increasing quorum sensing
C) triggering the production of streamers
D) digesting matrix molecules
E) stimulating quorum sensing receptors

Question 32

MacConkey agar plates represent medium.

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

Question 33

The best method for preserving bacterial cells in storage for decades is

A) lyophilization.
B) deep freezing.
C) refrigeration.
D) drying under anaerobic conditions.
E) storing them in shrink-wrap.

Question 34

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

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

Question 35

The method provides an estimate of the CFUs (colony -forming units) in a sample.

A) direct microscopic-count
B) streak-plate
C) turbidity
D) viable plate-count
E) Coulter counter

Question 36

Bacterial binary fission results in growth.

A) linear
B) exponential
C) arithmetic
D) stationary
E) binary

Question 37

The generation time of bacterial cells is shortest during the

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

Question 38

A Petroff-Hauser counting chamber is a(n)

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

Question 39

Which of the following is an indirect method for estimating the number of microbes in a sample?

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

Question 40

During which growth phase do antimicrobial drugs have the greatest inhibitory effect?

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

Question 41

Halophiles are found living in high conditions.

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

Question 42

Biofilms are the natural state for the majority of bacteria in nature.

Question 43

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

Question 44

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

Question 45

An obligate anaerobe can be cultured in a candle jar.

Question 46

Flow cytometry is an indirect method of determining the number of cells in a sample.

Question 47

The generation time of a bacterial culture is determined by the culture conditions.

Question 48

The conversion of nitrogen gas to ammonia is called nitrogen (metabolism/fixation).

Question 49

Serial dilution can be used in combination with pour plates as a method for isolating pure cultures.

Question 50

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

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

Question 51

The (optimum/range/minimum) growth temperature is the temperature at which an organism exhibits the highest growth rate.

Question 52

A 100 μl sample containing 1000 bacterial cells/μl in log phase growth is added to 9.9 ml of fresh culture medium broth. Assuming no nutrients are in limited supply, and a generation time of 30 minutes, how many bacteria will be present in the entire broth culture after six hours?

Question 53

The preferred method for long term storage of bacteria is (freezing/refrigeration/lyophilization).

Question 54

Nitrogen fixation produces ammonia from amino acids.

Question 55

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

Question 56

Organisms that require organic sources of carbon and energy are called (chemoheterotrophs/chemoautotrophs/auxotrophs).

Question 57

Microaerophiles are microbes that grow best at low

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

Question 58

Reactions catalyzed by superoxide dismutases can produce the (hydroxyl/peroxide/superoxide) radical.

Question 59

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

Question 60

A laboratory protocol lists the following ingredients: 1 g sucrose, 16.4 g Na 2HPO4, 1.5 g (NH4)3PO4, 0.02 g CaCO3, KNO3, water to 1 liter and autoclave. This recipe is for a medium.

A) complex broth
B) defined agar
C) defined broth
D) complex enrichment broth
E) reducing agar

Question 61

A(n) (culture/specimen/inoculum) is a sample of microorganisms introduced into a growth medium.

Question 62

Many photosynthetic organisms produce (catalase/carotenoids/dismutase) to protect themselves from the damaging effects of singlet oxygen (1O2).

Question 63

Alkalinophiles can survive in water up to pH (11.5/10/7.0).

Question 64

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

Question 65

Growing viruses in the lab requires (cell/enrichment/differential) culturing.

Question 66

Flow (spectrophotometry/cytometry) is a method of counting cells that have been stained or tagged with fluorescent dyes.

Question 67

A clinical sample of (urine/sputum/tissue) is called a biopsy.

Question 68

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 69

A pure culture is composed of cells that arise from a single (cell/inoculum/sample).

Question 70

A (Coulter counter/cytometer/spectrophotometer) can measure changes in the turbidity of a bacterial culture.

Question 71

A growth curve plots the (number/concentration) of viable organisms in a growing population over time.

Question 72

A sample placed into fresh medium is initially in the (lag/log/stationary) phase of microbial growth in most instances.

Question 73

A new prokaryote is recovered from a remote saline hot spring. Design a set of experiments to determine whether the organism is thermophilic or thermoduric, halophilic or halotolerant.

Question 74

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

Question 75

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