BIO 250 HW #2

A nurse takes a urine sample from a patient suspected of having contracted a urinary tract infection. The nurse uses careful aseptic technique in collecting the sample. Which is NOT a reason for using aseptic technique in this situation? A. The nurse wants to get as many organisms as possible to grow in the culture medium. B. The nurse wants to avoid contamination of the urine by microbes from the air, the nurse, or the environment. C. The nurse wants only the organisms in the urine to be cultured in the medium. D. The nurse wants to avoid contamination of the nurse, the patient, or the environment by the urine organisms.

A. The nurse wants to get as many organisms as possible to grow in the culture medium.

Cultures of a bacterial species were incubated on the shelf of a refrigerator (5°C), on a lab benchtop (25°C), on the shelf of a 37°C incubator, and on the shelf of a 50°C incubator. After incubation, there was no growth at 37°C or 50°C, slight growth on the benchtop, and abundant growth at refrigeration. What term could be used for this species? A. psychrophile B. anaerobe C. mesophile D. halophile

A. psychrophile

Which of the following statements is FALSE? A. The generation time of bacteria may vary from species to species. B. In the lag phase, cell death exceeds cell division. C. In the death phase, bacterial growth may cease as a result of oxygen and nutrient depletion. D. Bacteria typically divide by binary fission, producing two daughter cells.

B. In the lag phase, cell death exceeds cell division.

The optimal growth temperature of a bacterium is most closely related to the optimal temperature for A. transcription of DNA. B. enzyme function. C. DNA replication. D. mRNA attachment to ribosomes.

B. enzyme function.

When counting colonies on an agar plate A. only viable colonies are counted. B. it is assumed that each colony arose from division of one or a few cells. C. the medium must be suitable for colony growth. D. All of these answer choices are true.

B. it is assumed that each colony arose from division of one or a few cells.

The time between inoculation and the beginning of growth is usually called the A. death phase. B. lag phase. C. log phase. D. dormant phase.

B. lag phase.

Cell density in a chemostat is controlled by A. the size of the initial inoculum. B. the concentration of the limiting nutrient. C. the concentration of the limiting nutrient, the dilution factor, and the size of the initial inoculum. D. the dilution factor.

B. the concentration of the limiting nutrient.

An agar plate for counting colonies and maximizing statistical validity should ideally contain A. 100 to 1000 colonies. B. 50 to 100 colonies. C. 30 to 300 colonies. D. 1 to 100 colonies.

C. 30 to 300 colonies.

Bacterial growth refers to A. the time required for one cell to divide into two. B. the occurrence of mitosis. C. an increase in the number of cells. D. the occurrence of binary fission.

C. an increase in the number of cells.

A medium containing known substances in precise amounts is known as a ________ media. A. selective B. natural C. defined D. complex

C. defined

The time interval required for the formation of two cells from one is called the A. growth rate. B. growth time. C. generation time. D. division rate.

C. generation time.

Turbidity measurements are commonly utilized for monitoring A. conies. B. sessile cultures. C. planktonic cultures. D. biofilms.

C. planktonic cultures.

Selective medium differs from differential medium because A. differential medium contains growth inhibitors while selective medium does not. B. differential medium differentiates pathogens from nonpathogens while selective medium grows only pathogens. C. selective medium permits growth of a particular microbial type while differential medium is used to distinguish between types of organisms. D. selective medium permits growth of more organisms than differential medium.

C. selective medium permits growth of a particular microbial type while differential medium is used to distinguish between types of organisms.

Serial dilutions are generally made A. to reach a suitable dilution while minimizing error. B. when the appropriate viable count is unknown. C. based on powers of 10, although other serial dilution factors are possible. D. All of these answer choices apply.

D. All of these answer choices apply.

A microbe growing in a refrigerator is likely A. mesophilic. B. hyperthermophilic. C. psychrophilic. D. psychrotolerant or psychrophilic.

D. psychrotolerant or psychrophilic.

A bacterial cell in nutrient broth with a generation time of 15 minutes will produce 16 cells in 2 hours. True or False

False

A bacterium whose optimal growth temperature is 35C would be classified as a thermophile. True or False

False

A complex medium is one that has been completely made in the laboratory and the concentration of all the nutrients is known. True or False

False

Direct microscopic counting of cells is an accurate method for estimating the number of viable cells in a sample. True or False

False

Irreversible cell damage is more likely to occur at low rather than high temperatures. True or False

False

Mesophiles typically have longer fatty acid tails and more saturated carbon-carbon bonds in their cytoplasmic tails compared with thermophiles. True or False

False

The death phase applies to individual cells rather than populations. True or False

False

A bacterium such as a snow alga that is able to grow in cold temperatures is called a psychrophile. True or False

True

Planktonic cells remain in suspension while sessile cells adhere to a surface. True or False

True

Some microbes can grow in boiling water. True or False

True