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Microbiology > Exam 2- Growth > Flashcards

Exam 2- Growth Flashcards

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Biology 101 flashcards
1
Q

What is culture medium?

A

nutrients prepared for microbial growth

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2
Q

What does it mean to inoculate something?

A

to intentionally introduce microbes into medium

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3
Q

What is a culture?

A

microbes growing in or on a medium

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4
Q

What is a pure culture?

A

a genetically homogeneous population of microbes

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5
Q

What does sterile mean?

A

no viable organisms in or on a medium or object (including endospores & viruses)

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6
Q

What is a chemically defined media?

A

when the exact chemical composition is known

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7
Q

What is a complex media?

A

when the exact composition is not known

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8
Q

What is agar?

A

a complex polysaccharide that is commonly used to solidify media

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9
Q

Why do we use agar?

A
  1. nontoxic to most microbes
  2. not metabolized by most microbes
  3. stable in the autoclave
  4. once solidified at 40C it remains sold over a wide range of temps.
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10
Q

What is a colony?

A

a visible mass of cells arising from a single cell

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11
Q

What is a colony often called?

A

a colony-forming unit (CFU)

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12
Q

What is the streak plate method used for?

A

to isolate pure cultures

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13
Q

What does selective media mean?

A

to suppress unwanted microbes & encourage desired microbes

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14
Q

What is enrichment media?

A

used to increase numbers of desired organism to detectable levels

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15
Q

What is differential media used for?

A

to expose biochemical differences between species that grow equally well

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16
Q

What is in mannitol salt agar?

A

sodium chloride, D-Mannitol, & Phenol red

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17
Q

Describe binary fission.

A

where one parent cell splits into two daughter cells

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18
Q

What happens during exponential growth?

A

population size doubles at a fixed rate

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19
Q

What generates an exponential curve?

A

plotting the increase in the number of cells over time

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20
Q

How is growth plotted?

A

on a semi-log scale

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21
Q

Why is exponential growth no indefinite?

A

because nutrient consumption & toxic by-products eventually slow the growth rate until is halts

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22
Q

What happens when medium conditions deteriorate?

A

alterations occur in membrane composition, cell size, & metabolic pathways, all of which impact generation time

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23
Q

Explain a batch culture.

A

a liquid medium within a closed system

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24
Q

Explain a continuous culture.

A

an open system where fresh medium is continually added & spent medium removed

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25
Q

What does a continuous culture support?

A

prolonged exponential growth

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26
Q

Explain direct counts.

A

microorganisms can be counted directly by placing dilutions on a special microscope slide called a Petroff-Hausser counting chamber

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27
Q

What is a viable bacterium capable of?

A

dividing & forming a colony on a solid medium

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28
Q

When is counting bacteria by filtration used?

A

when quantities of bacteria are low

29
Q

What does turbidity mean?

A

cloudiness

30
Q

How can the number of cells be estimated?

A

by measuring the turbidity of a cell culture

31
Q

What factors can affect growth of microbes?

A

pH, temperature, pressure, & osmolarity

32
Q

What are extremophiles?

A

microbes that can grow in extreme environment

33
Q

What environments are considered extreme?

A

outside normal human habitats

34
Q

What are proteins & other macromolecular structures within the cell are affected by?

A

environmental change

35
Q

Why can’t microbes control their temperature?

A

bacterial temperature matches temperature in the immediate environment

36
Q

What does temperature affect?

A

the rate of motion, membrane fluidity, nutrient transport, DNA/RNA stability, & enzyme structure & function

37
Q

Explain psychrophiles.

A

organisms capable of growth in cold temperatures (0-21C, optimum 14C)

38
Q

Explain mesophiles.

A

microorganisms capable of growth at moderate temperatures (15-45C, opt. 20-40C)

39
Q

Explain thermophiles.

A

heat-loving organisms (50-have 80C)

40
Q

Explain hyperthermophiles.

A

microorganisms capable of growth at very hot temperatures (65-121C)

41
Q

What happens to enzymes at high temperatures?

A

they can denature

42
Q

Describe Listeria monocytogenes.

A

listeriosis, gram-positive, non-spore-forming bacteria, can grow & divide at 4C, food-borne pathogen

43
Q

What do lyophilization mean?

A

freeze-drying- frozen & dehydrated in a vacuum

44
Q

What is water activity a measure of?

A

water availability

45
Q

What decreases water activity?

A

interactions with solutes

46
Q

What is osmolarity a measure of?

A

the number of solute molecules in a solution

47
Q

What are halophiles?

A

species that require high salt concentrations

48
Q

What salt concentrations do most bacteria prefer?

A

concentrations at 0.05-1M (0.2-5%)

49
Q

What pH do most bacteria grow?

A

between 6.5 & 7.5

50
Q

What can changes in pH alter?

A

protein structure

51
Q

Describe Helicobacter pylori.

A

ancient symbiont, gram negative, proteobacteria, urease positive

52
Q

What are aerobes?

A

use oxygen as terminal electron acceptor in the electron transport chain to extract energy trapped in nutrients

53
Q

What are reactive oxygen species?

A

oxygen molecules or ions with one too few or too many electrons

54
Q

What forms of oxygen are very reactive & toxic to cells?

A

Superoxide free radicals, Peroxide anion, Hydroxyl radical

55
Q

What are strict aerobes?

A

aerobes that grow only when oxygen is present & consume oxygen during metabolism

56
Q

What are strict anaerobes?

A

anaerobes that die in small amounts of oxygen, do not use oxygen as an electron acceptor, generally obtain oxygen atoms from water.

57
Q

Explain facultative anaerobes.

A

possess enzymes to detoxify oxygen radicals & also machinery for bother fermentation & aerobic respiration

58
Q

Discribe aerotolerant anaerobes.

A

use only fermentation to provide energy but contain superoxide dismutase & catalase or peroxidase to protect them from ROS

59
Q

Describe microaerophiles.

A

will grow only at lo oxygen concentrations, possess decreased level of superoxide dismutase &/or catalase

60
Q

Describe endospores.

A

highly differentiated cells resistant to heat, desiccation, harsh chemicals, radiation

61
Q

What does dormant mean?

A

not metabolically active

62
Q

What is germination generally triggered by?

A

heat & amino acids

63
Q

What can sporulation be triggered by?

A

starvation

64
Q

Explain spore structure.

A

makes the spore resistant to many environmental stresses that kill vegetative cells

65
Q

What is a biofilm?

A

a mass of bacteria that stick to & multiply on a solid surface

66
Q

What do microbes in a biofilm do?

A

share nutrients

67
Q

What does formation of a biofilm involve?

A

quorum sensing

68
Q

What is quorum sensing?

A

where bacteria measure population size through the sending & receiving of chemical signals.

Microbiology (11 decks)

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