Microbial growth

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Microbiology
Chapter 6
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1

Figure 6.1, which line best depicts a facultative anaerobe in the absence of O2?

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B

2

In figure 6.1, which line best depicts an obligate anaerobe in the presence of O2?

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C

3

In figure 6.1, which line shows the growth of an obligate aerobe incubated anaerobically

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C

4

In figure 6.1, which line best illustrates the growth of a facultative anaerobe incubated aerobically

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A

5

In figure 6.1, which line best depicts a psychrotroph incubated at 0 degree Celsius

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B

6

If cells are grown in media containing amino acids labeled with radioactive nitrogen, most of the radioactivity will be found in the cells'

DNA and proteins

7

Which of the following elements is NOT correctly matched with its cellular function

phosphorous - Used for production of carbohydrates

8

Pathogenic bacteria isolated from the respiratory or intestinal tracts of humans are

Capnophiles that grow best in carbon dioxide incubators

9

A sample of milk tested for its bacterial content in a plate count assay. a one-milliliter sample of the milk is diluted in a 1:10 dilution series. One milliliter of the third dilution tube is plated in a pour plate. After incubation, the plate has 54 colonies, indicating that the original milk sample contained

54,000 cells per milliliter

10

The addition of which of the following to a culture medium will neutralize acides

buffers

11

salts and sugars work to preserve foods by creating a

hypertonic environment

12

the term aerotolerant anaerobe refers to an organism that

does not use oxygen but tolerates it

13

Which of the following is an advantage of the standard plate count

determines the number of viable cells

14

Which of the following is an advantage of the direct microscopic count

requires no incubation time

15

quorum sensing

cell-to-cell chemical communication

allows bacteria to coordinate their activity and group together

16

thirty-six colonies grew in nutrient agar from 1.0ml of undiluted sample in a standard plate count. How many cells were in the original sample

36 per milliliter

17

figure 6.2 shows a typical bacterial growth curve with the y-axis indicating the lof of the number of bacteria and the x-axis indicating time in culture. In the figure, which section shows a growth phase where the number of cells dying equals the number of cells dividing

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C

18

figure 6.2 shows a typical bacterial growth curve with the y-axis indicating the log of the number of bacteria and x-axis indicating time in culture. IN the figure, which sections of the graph illustrate a logarithmic change in cell numbers

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B

19

Most bacteria grow best at pH

7

20

Most fungi grow best at pH

5

21

consider a culture medium on which only gram-positive organism such at Staphylococcus aureus colonies can grow due to an elevated NaCl level. A yellow halo surrounds the growth, indicating the bacterium fermented a sugar in the medium, decreasing the pH as a result and changing the color of a pH indicator chemical. This type of medium would be referred to as an

selective and differential medium

22

a culture medium consisting of agar, peptone, and beef heart, is a

complex medium

23

Which of the following pairs of microbe classification terms and optimal growth temperatures is mismatched

thermophile - growth at 37 degrees celsius

24

during which growth phase will gram-positive bacteria be most susceptible to penicillin

log phase

25

which of the following is the best definition of generation time

the length of time needed for a cell to divide

26

which of the following is not a direct method to measure microbial growth

metabolic activity

27

which group of microorganisms is most likely to spoil a freshwater trout preserved with salt

facultative halophiles

28

which of the following is an organic growth factor

vitamin B1

29

which of the following is an example of metabolic activity that could be used to measure microbial growth

glucose consumption

30

an experiment began with 4 cells and ended with 128 cells. How many generations did the cells go through

5

31

three cells with generation times of 60 minutes are inoculated into a culture medium. How many cell are there after 5 hours

96

32

In figure 6.3 which tube shows the expected growth pattern for a microaerophile

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E

33

in figure 6.3 which tube shows the expected growth pattern for facultative anaerobe

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B

34

In one hospital, Pseudomonas aeruginosa seroptype 10 infected the biliary tract of 10% of 1300 patients, who underwent gastrointestinal endoscopic procedures. After each use, endoscopes were washed with an automatic reprocessor that flushed detergent and glutaraldehyde through the endoscopes, followd by a tap water rinse. P. aeruginosa serotype 10 was not isolated from the detergent, gluataraldehyde, or tap water. What was the source of the infections

a biofilm in the reprocessor

35

for the three types of media, which medium (or media) is/are chemically defined

Medium A

36

in which medium (or media) would an autotroph grow

Medium A

37

Assume you inoculated 100 cells, with a generation time of 20 minutes, into 100ml of nutrient broth. You then inoculated 100 cells of the same species into 200ml of nutrient broth. After incubation for 4 hours, you can reasonably expect to have

the same number of cells in both

38

The source of nutrients in nutrient agar is

peptone and beef extract

39

which enzyme catalyzes the reaction O2- + O2- + 2H+ → H2O2 + O2?

superoxide dismutase (SOD)

40

Which enzyme catalyzes the reaction: 2H2O2 → 2H2O + O2?

catalase

41

Which enzyme catalyzes the reaction: H2O2 + 2H+ → 2H2O?

peroxidase

42

the data in table 6.2 indicate that S. aureus is a(n)

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facultative halophile

43

Patients with indwelling catheters are susceptible to infections because

biofilms develop on catheters

44

an isolated colony on a streak plate contains millions (or even billions) of identical cells all arising from one initial cell

true

45

bacterial growth refers to an increase in the numbers of cells in a bacterial culture

true

46

pure cultures can easily be obtained on streak plates, even if the desired bacteria are present in very low concentrations in the initial culture broth

false

47

agar is used as a solidifying agent in microbiological media since few bacteria can degrade it

true

48

laboratory cultivation of obligate anaerobes requires reducing media or special growth chambers filled with inert gases

true

49

most pathogenic bacteria are thermophiles

false

50

in performing a ten-fold dilutions series from a sample containing 10,000 bacteria per milliliter, the fourth tube in the dilution series will have 10 cells per milliliter

false

51

What are the physical requirements for growth?

temperature

pH

osmotic pressure

52

What are the chemical requirements for growth

Carbon

nitrogen, sulfur, phosphorus

trace elements

oxygen

organic growth factors

53

what are the 3 groups based on range of temperature

psychrophiles

mesophiles

thermophiles

54

psychrophiles

cold-loving microbes

-10 - 20oC

55

mesophiles

moderate-temperature loving

10 - 30oC

56

Thermophiles

heat-loving

50-60oC

57

minimum growth temperature

lowest temperature at which species will grow

58

optimum growth temperature

temperature at which species grow best

59

maximum growth temperature

highest temperature at which growth is possible

60

psychrotrophs

can grow at 20 - 30oC temperatur. Found in low temperature food spoilage

61

hyperthermophiles

optimum growth temperature of 80 oC or higher.

sulfur is important in metabolic activity

62

pH

acidity or alkalinity of a solution

bacteria grow best between pH 6.5 and 7.5

63

osmotic pressure

plasmolysis - shrinkage of cell's cytoplasm

high salt or sugar concentrations draw water out of microbial cells and prevents their growth

microorganism require water for growth. their composition is 80-90% water

64

extreme halophiles

high salt concentrations. organisms require 30% salt

65

falcultative halophiles

do not require high salt concentrations

66

carbon

needed for all organic compounds that make up a living cell.

one of the most important requirements for microbial growth

67

nitrogen, sulfur and phosphorus

nitrogen is used to form amino group

sulfur is used to synthesize sulfur-containing amino acids and vitamins

phosphorus is used for the synthesis of nucleic acids and phospholipids of cell membranes

68

nitrogen fixation

using gaseous nitrogen directly from the atmosphere

69

obligate aerobes

organisms that require oxygen to live

70

facultative anaerobes

ability to grow in the absence of oxygen

71

obligate anaerobes

bacteria that are unable to use molecular oxygen for energy-yielding reactions

72

how microorganisms can be harmed by O2

singlet oxygen

superoxide radicals

peroxide anion

hydroxyl radical

73

organic growth factors

essential organic compounds an organism is unable to synthesize

must be directly obtained from the environment b

74

biofilms

thin, slimy layer encasing bacteria that adheres to a surface

can be considered a hydrogel

75

quorum sensing

cell-to-sell chemical communication

allows bacteria to coordinate their activity and group together

76

growth rates of different types of microorganisms in response to temperature

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77

culture media

nutrients prepared for microbial growth

78

inoculum

microbes that are introduced into a culture medium to initiate growth

79

culture

microbes that grow and multiply in or on a culture medium

80

criteria for culture medium

must contain the right nutrients for the specific microorganism growing

should contain sufficient moisture, properly adjusted pH, and suitable level of O2

must be sterile

81

sterile

must contain no living microorganism

82

agar

solidifying agent

liquefies at 1000C and solidifies at ~ 400C

83

chemically defined media

one whose exact chemical composition is known

medium must provide an energy source

organism that require many growth factors are fastidious

84

complex media

made up of nutrients including extracts from yeast, meats, or plants

85

anaerobic growth media and methods

reducing media is used because anaerobes might be killed by exposure to oxygen. Medium contains sodium thioglycolate that chemically combine with dissolved oxygen and deplete oxygen in the culture medium.

86

capnophiles

microbes that can grow better at high CO2 concentrations

87

selective media

designed to suppress the growth of unwanted bacteria and encourage the growth of desire microbes

88

differential media

makes it easier to distinguish colonies of desired organisms from unnecessary ones

89

enrichment culture

designed to increase very small numbers of the desired type of organism to detectable levels

90

reducing media

takes away the oxygen

anaerobic bacteria grows in ot

91

gas gangreen

anaerobes produces to protect itself

92

anaerobic chamber

takes away O2 and creates CO2

93

generation time

time required for a cell to divide

generation number is the exponent

94

phases of growth

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