Question

1.   Which is not true about autoclaving?

a. Autoclaving requires steam under pressure

b. Autoclaving requires maintaining steam at 121oC and 15 psi for

15 minutes

c. It is an effective way to pasteurize milk and other liquids

d. Steam must come in contact with the surface of the substance being sterilized

2.     We wished to determine the abundance of bacteria in a sample of milk. To do this ten-fold serial dilutions of a one milliliter milk sample were prepared. One milliliter of the third dilution was plated in a pour plate. After incubation, the plate had 54 colonies. How many bacteria were in the original milk sample?

a. 54 cells per ml

b. 540 cells per ml

c. 5,400 cells per ml

d. 54,000 cells per ml e. 540,000 cells per ml

3.   Bacteriostatic compounds

a. are biological or chemical agents that stop bacteria from

reproducing.

b. are biological or chemical agents that kill bacteria. c. create static electricity that inhibits the growth of

bacteria.

d. answers (a) and (c) are correct.

4.   Bactericidal compounds

a. are biological or chemical agents that stop bacteria from reproducing

b. are biological or chemical agents that kill bacteria

c. are suicidal compounds that become inactive over time d. answer (b) and (c) are correct

5.   Antisepsis is

a. killing harmful microorganisms on the surface of materials. b. killing bacteria that form endospores.

c. destroying harmful microorganisms in living tissue.

d. killing all microorganisms.

6.   Low temperatures

a. have a bacteriostatic effect on most bacteria. b. result in desiccation of bacteria.

c. remove water from the environment and thereby prevent bacterial metabolism.

d. create a hypertonic environment causing plasmolysis.

7.     An isolated colony on a streak plate contains millions (or even billions) of identical cells that all grew from a single cell. a. This is a false statement

b. This is partly false, because it takes more than one cell to form a colony

c. This is a true statement

d. This is almost correct, but the colony would only have hundreds of cells.

8.     Which of the following are environmental factors that influence microbial growth?

a. oxygen

b. temperature

c. osmotic pressure

d. the kinds and concentrations of available nutrients

e. all of the above

9.   Oxygen

a. is required for strictly aerobic bacteria. b. can be toxic or lethal to some organisms.

c. toxicity mostly due to the production of superoxide radicals that are powerful oxidizing agents.

d. aerobic bacteria can protect themselves but strict anaerobes can not.

e. all of the above.

10. Which kind of organism is killed by atmospheric oxygen?

a. facultative anaerobes b. obligate aerobes

c. obligate anaerobes

d. aerotolerant anaerobes

11.    Toxic hydrogen peroxide produced in some bacteria can be broken down into water and oxygen by which enzyme?

a. superoxide dismutase b. peroxidase

c. hydroxylase

d. catalase

12.    Which of the following is not likely to be a reason for why exponential growth stops?

a. accumulation of waste products b. exhaustion of nutrients

c. harmful changes in pH

d. bacteria becoming dormant

13. In the stationary phase of growth in batch cultures

a. the number of microbial deaths exceeds the number of new cells formed

b. the number of microbial deaths is equal to the number of new

cells formed

c. new cells are no longer formed because of adverse

environmental conditions

d. cellular reproduction is most active

14.    The removal or destruction of all microorganisms is called a. sterilization

b. disinfection

c. pasteurization

d. sanitization

15.    If a population of 100,000 microbes has been treated with an antimicrobial chemical solution for two minutes and 90% of the population dies per minute, How many microbes remain after two minutes?

a. 100,000

b. 10,000 c. 1000

d. 100

16.    The surface of your kitchen counter has 108 bacteria so you clean it with a disinfectant that kills 99.9% of germs on contact. How many bacteria remain and are viable?

a. 107 b. 106 c. 105 d. 104

17. Which of the following are required for microbial cell growth?

a. reduced cofactors

b. anabolic intermediates

c. energy conserved in chemical bonds

d. only (b) and (c)

e. (a), (b) and (c) are all required

18.    A bacterial species has a generation time of 20 minutes and is growing exponentially. If there are 10 cells initially how many cells are there after 80 minutes?

a. 30

b. 80 c. 160 d. 200

e. none of the above

19.    The growth of almost all bacteria in the environment a. is limited by cool temperatures

b. is limited by high pH

c. is limited by the availability of one or more nutrients

d. is unlimited because bacteria are metabolically versatile

20. Pasteur used swan-necked flasks

a. to disprove the theory of spontaneous generation

b. to explain why wine was sometimes sour c. to demonstrate the cause of rabies

d. to demonstrate the effectiveness of pasteurization

21.    Antoni van Leeuwenhoek developed and used

a. the first compound microscope

b. the first vaccine to prevent an infectious disease

c. a microscope with a single lens

d. pasteurization to prevent the spoilage of food

Answer 1