Chapter 5 game show

Importing high concentrations of compatible solutes is a strategy cells use to counteract the effects of an environment containing a A. high salt concentration. B. high dissolved-oxygen C. concentration. D. high water potential. E. low ionic concentration.

A

The time required for a 10-fold reduction in the viability of a microbial population using a particular heating method is called the A. decimal reduction time. B. thermal death time. C. disinfection time. D. sterilization time.

A

Which of those listed below is NOT classified as a cardinal temperature? A. lethal temperature B. maximum temperature C. minimum temperature D. optimum temperature

A

________ and peroxidase both detoxify H2O2. A. Catalase B. Hydroxylase C. Oxide reductase D. Superoxide reductase

A

Why are serial dilutions often performed before aliquoting a sample of cells onto plates for counting colonies? A. The transferred spent media can affect growth and need to be diluted out. B. Otherwise the colonies would be too numerous to count. C. This dilution scheme decreases error. D. Both b and c are correct.

B

________ organisms have a particularly difficult time maintaining a proton motive force to synthesize ATP using ATP synthase. A. Acidophilic B. Alkaliphilic C. Microaerophilic D. Obligate anaerobic

B

Heat-sensitive liquids are typically sterilized by A. autoclaving. B. pasteurization. C. filtration. D. phenolic compounds.

C

Proteins in psychrophilic cells generally have ________ than proteins found in cells that grow optimally at higher temperatures. A. fewer α-helices and more β-sheets B. fewer hydrogen bonds C. more α-helices and fewer β-sheets D. more hydrogen bonds

C

The exact composition of ________ media is known. _______ media inhibit the growth of some microbes. ________ media are used to culture fastidious microbes, particularly pathogens. A. complex....Differential....Selective B. complex....Enriched....Differential C. defined....Selective....Enriched D. defined....Enriched....Differential

C

What happens when a culture is incubated above the organism's maximum temperature for growth? A. The cell continues to grow at the normal rate. B. The cells grow much faster than normal because the enzymatic reactions are occurring at a much faster rate. C. The cell membranes collapse, proteins denature, and the cell usually dies. D. The transport of nutrients into the cell is slow; therefore, the cells grow more slowly than normal.

C

Which of the following is NOT a drawback in using a microscope to count cells? A. Debris in the sample may be mistaken for microbial cells. B. Motile cells must be immobilized before counting. C. Cells are difficult to stain. D. Without specific stains, dead cells cannot be distinguished from live cells.

C

Which type of microorganism shows even growth throughout thioglycolate broth? A. obligate aerobe B. facultative aerobe C. aerotolerant anaerobe D. microaerophile

C

Which growth phase has the largest increase in cell numbers per unit of time? A. death phase B. exponential phase C. lag phase D. stationary phase

B

A product purchased from a drug store guaranteed to kill or inhibit bacteria on skin is best described as a(n) A. sanitizer. B. antiseptic. C. disinfectant. D. sterilant.

B

In a disc diffusion assay, the zone of inhibition will be ________ for organisms more resistant to an antimicrobial agent. A. absent B. smaller C. larger D. yellow

B

Microbes that naturally live within mammalian hosts are A. psychrotolerant. B. mesophiles. C. thermophiles. D. xerophiles.

B

To speed up the growth rate in a chemostat, the ________ should be increased. To increase the cell density as well, the ________ should be increased. A. dilution rate / dilution rate B. dilution rate / limiting nutrient C. limiting nutrient / dilution rate D. limiting nutrient / limiting nutrient

B

Turbidity of a liquid culture used to determine the cell number is most powerful when combined with a carefully constructed A. diffraction coefficient rate. B. growth curve relating OD to cell number. C. OD versus time graph. D. growth yield curve.

B

For which of the following populations/samples would it be MOST inappropriate to use the spread-plate technique to quantify viable cells? a. Escherichia coli K-12 b. Bacillus anthracis c. Haemophilus influenzae d. soil sample

D

Hyperthermophilic enzymes A. are often used commercially due to their high stability. B. have more ionic bonding between basic and acidic amino acids. C. have highly hydrophobic interiors to prevent unfolding. D. involve all of the above.

D

If a heterotrophic bacterium were grown in a minimal glucose medium and transferred during exponential growth phase into the complex LB medium, the cell would have a relatively A. short exponential phase because it already is in exponential growth phase. B. high growth yield compared to cells transferred during stationary growth phase. C. long lag phase because it has to adjust to a different chemical environment/medium. D. short lag phase because of the availability of amino acids and other nutrients.

D

In which growth phase is there no increase or decrease in cell number because some cells are dividing while others are dying? A. death phase B. exponential phase C. lag phase D. stationary phase

D

Maintaining a constant cell population in a chemostat requires the monitoring and control of A. nutrient concentrations. B. the dilution rate of volume pumped in. C. the population's waste products. D. all of the above.

D

Which type of microorganism would NOT be able to grow under anoxic conditions? A. aerotolerant anaerobe B. anaerobe C. facultative aerobe D. microaerophile

D

________ is used to reduce microbes in food products to increase shelf life, and ________ is routinely used to sterilize a variety of food products, surgical supplies, and laboratory equipment. A. Ionizing radiation....pasteurization B. UV radiation....cold sterilization C. Steam heat....UV radiation D. Pasteurization....ionizing radiation

D

True or False: Acidophiles maintain a cytoplasmic pH below 5.5. TRUE FALSE

false