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Microbial Nutrition & Growth
Which of the following pH levels would probably be lethal to an alkalinophile?
A. pH 10
B. pH 4
C. pH 8
D. pH 14
A cell which uses an organic carbon source and obtains energy from light would be called a(n)
A. chemoheterotroph.
B. photoautotroph.
C. chemoautotroph.
D. photoheterotroph.
Which of the following forms of oxygen is often used by phagocytic cells to destroy pathogens?
A. singlet oxygen
B. hydroxyl radicals
C. peroxide anions
D. superoxide radicals
These microbes do not have an aerobic metabolism, but they can detoxify oxygen enough to live in its
presence:
A. obligate anaerobes
B. facultative anaerobes
C. aerotolerant anaerobes
D. microaerophiles
Which of the following elements is often growth limiting for organisms because of its limited
availability?
A. nitrogen
B. hydrogen
C. oxygen
D. carbon
Organic molecules that organisms need, but cannot synthesize all by themselves, are called
A. trace elements.
B. carotenoids.
C. growth factors.
D. nutrients.
A microbe isolated from deep in the ocean could be characterized as a
A. barophile.
B. mesophile.
C. psychrophile.
D. Both A and C are correct.
E. A, B, and C are correct.
All of the following are true statements regarding clinical specimens EXCEPT:
A. Clinical specimens include saliva, feces, and blood.
B. Clinical specimens are often transported in special media to help preserve them.
C. Universal precautions are observed in order to protect specimens from contamination.
D. Clinical specimens must be properly labeled and promptly transported to the laboratory.
All of the following are associated with the streak plate method of isolation EXCEPT:
A. a sterile inoculating loop or needle.
B. isolation of CFU's from one another.
C. a solid medium in a Petri dish.
D. colonies growing at and below the surface of the medium.
Microbes living in geothermal springs are more likely to metabolize hydrogen than sulfur because
A. the by-products of sulfur metabolism are poisonous to them.
B. hydrogen is more plentiful in these environments than sulfur.
C. they cannot obtain enough oxygen to support sulfur metabolism.
D. they can obtain hydrogen from other microbes in their habitat.
Why is agar a useful substance in the microbiology lab?
A. Agar dissolves in water at about 60OC.
B. Solid agar melts at temperatures above 40OC.
C. Agar is a good source of nutrients for microbes.
D. Agar does not solidify until it cools to about 40O C.
All of the following are true statements concerning types of media EXCEPT:
A. A synthetic medium is the same thing as a defined medium.
B. Differential media often involve visible changes in the appearance of colonies.
C. Complex media often involve the addition of substances such as soy, yeast or blood.
D. Media can be either selective or differential, but not both.
Kineococcus radiotolerans is an example of which of the following?
A. a barophile
B. an extremophile
C. a psychrophile
D. a mesophile
The most destructive form of oxygen is
A. singlet oxygen.
B. the superoxide radical.
C. the hydroxyl radical.
D. the peroxide anion.
A bacterial species has been determined to have a generation time of 30 minutes. If a microbiologist
starts with an inoculum of 1000 cells/ml, and wants to grow it to a culture of 1,000,000 cells/ml,
approximately how long should the culture be incubated?
A. 24 hours
B. 3.5 hours
C. 5 hours
D. 100 hours
Why do bacterial cultures go through lag phase?
A. Because the DNA and protein synthesis in the culture has not caught up with cell division.
B. Because they are synthesizing new enzymes in order to use nutrients in their medium.
C. Because they are being exposed to increasing amounts of their own waste products.
D. Because they are gradually beginning to die.
All of the following statements concerning the bacterial growth curve are true EXCEPT:
A. When death phase is reached, all cells in the culture have died.
B. During stationary phase, the number of dying cells equals the number of cells being
produced.
C. Cells divide at a maximal rate during the log phase.
D. Under certain conditions, the log phase can be maintained indefinitely.
All of the following are direct methods of measuring microbial growth except:
A. turbidity.
B. membrane filtration.
C. viable plate counts.
D. a Coulter counter.
If a cell counter slide is determined to have a mean number of 20 bacterial cells per square, the total
number of bacteria per ml of culture would be:
A. 1,000,000
B. 25,000,000
C. 50,000,000
D. Unable to determine
All of the following are drawbacks to the use of spectrophotometry in estimating microbial growth
EXCEPT:
A. It will underestimate the true number of cells if they are not uniformly in suspension.
B. It kills the organisms as they are being counted.
C. It can not be used if there are less than one million cells per milliliter.
D. It cannot distinguish between live and dead cells.