MMBIO 221

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Microbiology
Chapters 5-7
Speed back Assignment 2
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1

A medium that contains yeast extract, glucose, and peptones would be a(n)

complex medium

2

A bacterial suspension produces a turbidity reading that corresponds to 5 x 107 CFU/ml. A viable plate count of the same suspension produces a concentration of only 1 x 105 CFU/ml. You most correctly conclude that

Turbidity is an accurate measure of concentration, but is measures both live and dead cells.

3

In metabolism, ______ reactions liberate energy used to make ATP, whereas ______ reactions require energy supplied by the hydrolysis of ATP.

catabolic, anabolic

4

The ATP made by oxidative phosphorylation

is powered by chemiosmosis using a proton gradient, is made at large transmembrane proteins called ATP syntheses, represents most of the energy made during respiration.

(all of the above)

5

Why are both the temperatures and times involved in hot air sterilization higher than those involved in steam sterilization?

Heat transfer is more efficient when water is involved.

6

At which phase of microbial growth is the growth rate identical to the death rate?

stationary phase

7

A bacterial growth experiment began with 100 cells and ended with 409,600 cells. How many generations occurred?

12

[Log (409,600) – Log (100)]/log 2 = 12, see Appendix B.

8

During glycolysis

ATP is generated by substrate-level phosphorylation.

9

Suppose you have a suspension of C. botulinum endospores that has a decimal reduction time (DRT) of 1.5 minutes at 121 °C. If you had 1 x 10 6 endospores, how long (at 121 °C ) would it take to reduce this number to a single organism?

9 minutes

10

The process of destroying vegetative pathogens on living tissue is most correctly called

antisepsis

11

What type of organism would have an optimum growth temperature at about 12 °C?

psychrophile

12

Plasmas, supercritical fluids, and peroxygens are all

new methods used to sterilize.

13

The most important products of the Krebs cycle are

NADH and FADH2.

14

The method of preserving bacterial cultures that involves sublimation is

lyophilization

15

The germicidal action of chlorine is due to the formation of

hypochlorous acid

16

The net yield of ATP equivalents from one turn of the Krebs cycle (starting with acetyl-CoA) is

12

17

The most common physical method of microbial control in foods is

heat treatment or low temperatures.

18

The most resistant microbe (of the ones listed) to chemical biocides is

bacterial endospores

19

A bacterostatic agent

inhibits the growth of bacteria.

20

Flavoproteins, cytochromes, and ubiquinones are all part of

the electron transport chain.

21

Phenolics, biguanides, halogens, alcohols, and probably quaternary ammonium compounds (Quats) all cause damage to the cell’s

plasma membrane.

22

Radiation does most of its lethal damage by causing breaks in, or changes to the microbe’s

DNA

23

Which of the following is not a common end product of a microbial fermentation?

Glucose

24

Organisms that grow deep in the bottom of the ocean (no light) next to hydrogen sulfide vents (source of energy), and are able to fix CO2 in the seawater, would be referred to as

chemoautotrophs

25

Which type of organism is indifferent to either the presence or absence of oxygen?

aerotolerant anaerobe

26

During photosynthesis, the main products of the light-dependent reactions are ________, whereas the main products of light-independent reactions are __________.

ATP, O2, and NADPH/sugars

27

Enzymes

lower the activation energy of a chemical reaction.

28

Five bacterial cells with a generation time of 15 minutes were allowed to grow for 8 hours. How many cells are present?

2.15 × 1010

Number of generations = 480/15 = 32; Nt = N0 x 2number of generations, = 5 x 232 = 2.15 x 1010, see Appendix B.

29

A sample of milk is diluted 1:2,000,000 and 1 ml samples of this dilution are plated in duplicate. The average plate count is 50 CFU. How many CFU/ml are present in the undiluted milk?

100,000,000

Total CFU/ml in milk = Ave. plate count x 1/dilution factor = 50 x 2,000,000 = 100,000,000 CFU/ml.

30

Blood agar containing an antibiotic that inhibits gram-positive organisms, would most correctly be called

both selective and differential.