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MCIM > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

bacteria reproduce by:

A

binary fission

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2
Q

time required for one binary fission event

A

generation time (G)

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3
Q

G depend on:

A

species, environment

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4
Q

why measure bacterial numbers?

A

monitor growth, diagnose, determine loads in food

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5
Q

methods for counting bacteria vary depending on:

A

living vs all, crude vs accurate, all or certain species

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6
Q

this method uses calibrated chamber and microscope to visually count all bacteria in liquid of known vol

A

direct microscopic count

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7
Q

pros of direct micro count?

A

simple and rapid

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8
Q

cons of direct micro?

A

crude, need large # cells for accuracy, can’t distinguish living/dead

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9
Q

based on concept that bacteria are particles that block light; amount of light blocked is proportional to # cells

A

turbidity

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10
Q

turbidity measured as

A

absorbance units in spectrophotometer

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11
Q

pros of turbidity?

A

fast, non-destructive, can follow growth in sample over period of time

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12
Q

cons of turbidity?

A

not sensitive, can’t distinguish live or dead

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13
Q

based on principle that each living cell in pop forms colony on solid media, uses dilution, spread on solid media, allow cells grow into colonies, count # of colonies

A

viable count (plate count)

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14
Q

bacterial concentration expressed as ___

A

Colony Forming Unit/mL (or L)

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15
Q

colonies on plate x ____ = # bacteria (CFU)/mL

A

dilution factor

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16
Q

pros of viable count:

A

very sensitive, widely used in food industry and clinical lab where number of live bacteria super important

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17
Q

cons of viable count:

A

very slow, some bacteria not easily or cannot be grown (underestimates)

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18
Q

to carry out binary fission, all bacteria need:

A

nutrients, water, proper pH, proper temp, proper gas atm

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19
Q

nutrients provide sources of :

A

carbon and minerals

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20
Q

most bacteria obtain all required nutr and gen nrg from breakdown of :

A

organic materials

21
Q

can use any one of >90 diff org nutr

A

pseudomonas

22
Q

can only use urea for growth

A

bacillus fastidiosus

23
Q

requires complex factors in host cell

A

chlamydia

24
Q

needs only water, minerals, and gluc

A

e. coli

25
Q

is it better use lots diff nutr, or only a few?

A

depends: if break lots, need lots of machinery, less streamlined, but can grow on lots of things so more versatile

26
Q

solvent which biocules dissolved

A

solvent

27
Q

bacterial cells are ___% water

A

80

28
Q

amount of free (unbound) water in substance

A

water activity

29
Q

reduces amt of free water available

A

dissolved solutes

30
Q

Aw outside cell is lower than inside cell

A

hypertonic

31
Q

what happens when hypertonic?

A

cytoplasm dehydrates in plasmolysis

32
Q

most bacteria only grow within Aw range of :

A

0.9-0.99

33
Q

exceptions of bacteria for Aw range?

A

osmotolerant (Aw 0.87, 20% NaCl); halophiles (40% NaCl)

34
Q

example of osmotolerant?

A

staph

35
Q

ex. of halophile?

A

archaea

36
Q

bacterial growth not happen if < ___ Aw

A

0.5

37
Q

why fungi more likely cause food spoil?

A

grow at lower Aw

38
Q

best growth occurs at this one temp

A

optimum temp

39
Q

opt. 10 degrees, food spoilage

A

psychrophiles

40
Q

opt. 37 degrees, majority of species

A

mesophiles

41
Q

opt. 70 degrees, compost/hot springs

A

thermophiles

42
Q

opt. >80 degrees, deep ocean thermal vent

A

extreme thermophiles

43
Q

most human pathogens don’t grow at

A

20

44
Q

significance of growth temp:

A

food preservation, disease (leprosy infect cool sites around 25degrees; therapy before antibiotics)

45
Q

(malaria) syphilis induce fever to prevent growth of ___

A

treponema

46
Q

why anthrax not affect chickens?

A

cuz normal body temp of chicken too high

47
Q

aerobes contain:

A

detoxifying enzymes to get rid of SO free radical produced during metabolism

48
Q

anaerobes don’t have these:

A

SOD and catalase

49
Q

why fill aerobic bottle first and anaerobic bottle last?

A

will introduce air in tube into bottle of anaerobic if do that first

MCIM (24 decks)

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