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microbiology > Ch. 9: Microbial Growth > Flashcards

Ch. 9: Microbial Growth Flashcards

1
Q

Binary fission

A

most common mechanism of cell replication in bacteria

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2
Q

FtsZ protein

A

directs process of cytokinesis & cell division

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3
Q

Z ring

A

anchored by FtsZ binding proteins & defines the division plane between the two daughter cells

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4
Q

Septum

A

a peptidoglycan cell wall that divides the two daughter cells

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5
Q

Generation time

A

the time between the same points of a life cycle in 2 generations

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6
Q

Doubling time

A

time it takes for a population to double through 1 round of binary fission; also called generation time in prokaryotes

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7
Q

Growth curve

A

a graph modeling # of cells in a culture over time

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8
Q

Culture density

A

defined as number of cells per unit volume

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9
Q

Inoculum

A

a small number of cells; beginning of the growth curve

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10
Q

Culture medium

A

a nutritional broth that supports growth

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11
Q

The lag phase

A

initial phase of growth curve; cells are gearing up for next phase of growth

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12
Q

The log phase

A

cells are actively dividing by binary fission & their numbers increase exponentially
- stage where bacteria are most susceptible to action of disinfectants & antibiotics that affect protein, DNA, & cell wall synthesis

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13
Q

Stationary phase

A

waste products accumulate, nutrients gradually used up, total number of live cells reaches a plateau

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14
Q

Death (decline) phase

A

number of dying cells exceeds number if dividing cells, leading to exponential decrease in total number of cells

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15
Q

Intrinsic growth rate

A

generation time under specific growth conditions (nutrients, pH, temp, etc.) is genetically determined

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16
Q

Persisters

A

these few cells are characterized by a slow metabolic rate
- medically important because they are associated with chronic infections that don’t respond to antibiotic treatment

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17
Q

Direct microscopic cell count

A
  • simplest way to count bacteria
  • involves transferring a known volume of a culture to a calibrated slide & counting the cells under a light microscope
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18
Q

Petroff-Hausser Chamber

A

calibrated slide used in a direct microscopic cell count

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19
Q

Viable cells

A

live cells

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20
Q

Viable plate count

A

a count of viable or live cells

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21
Q

Colony forming unit

A

results of a count usually expressed this way because more than one cell may be in the same spot

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22
Q

Serial dilution

A

process used to obtain plates with CFUs in range 30-300; process usually involves several dilution of multiples of 10 to simply calculations

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23
Q

Pour plate method

A

sample mixed in warm liquid agar & poured into sterile petri dish, mixed by swirling, solidifies and is incubated, resulting colonies counted

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24
Q

Spread plate method

A

sample poured onto solid agar, spread onto agar using sterile spreader, incubated & resulting colonies counted

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25
Q

Membrane filtration technique

A

known volumes are vacuum filtered aseptically through membrane with pore size small enough to trap microorganisms; membrane transferred to Petri plate containing appropriate growth medium; colonies counted after incubation

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26
Q

Most probable number (MPN) method

A

statistical procedure for estimating the number of viable microorganisms in a sample

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27
Q

Turbidity

A

cloudiness of a sample

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28
Q

Fragmentation

A

new cells splitting from parent filament and floating away

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29
Q

Budding

A

tip of extension swells and forms a smaller cell (the bud) that eventually detaches from parent cell

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30
Q

Biofilms

A

complex and dynamic ecosystems that form on a variety of environmental surfaces

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31
Q

Extracellular polymeric substances (EPS)

A

composes the extracellular matrix, secreted by organisms in biofilm

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32
Q

Planktonic cells

A

free floating microbial cells that live in aquatic environments

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33
Q

Sessile

A

attached to a surface

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34
Q

Quorum sensing

A
  • can occur between cells of different species within a biofilm
  • enables microorganisms to detect their cell density through the release & binding of small diffusible molecules called autoinducers
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35
Q

Autoinducers

A

signaling molecule produced by a bacterial cell that can modify the activity of surrounding cells

36
Q

Reactive oxygen species (ROS)

A

highly unstable ions & molecules derived from partial reduction of oxygen that can damage virtually any macromolecule or structure with which they come in contact

37
Q

Thioglycolate tube cultures

A

starts with autoclaved thioglycolate medium, tubes inoculated and incubated

38
Q

Thioglycolate medium

A

contains low percentage of agar to allow motile bacteria to move throughout medium

39
Q

Anaerobic jar

A

include chemical packs that remove oxygen and release carbon dioxide; anaerobic bacteria must be grown in these

40
Q

Anaerobic chamber

A

an enclosed box from which all oxygen is removed; gloves seal opening in box, allowing handling of cultures inside the box

41
Q

Optimum oxygen concentration

A

the ideal oxygen concentration for a particular microorganism

42
Q

Minimum permissive oxygen concentration

A

lowest concentration of oxygen that allows growth

43
Q

Maximum permissive oxygen concentration

A

highest tolerated concentration of oxygen

44
Q

Peroxidase

A
45
Q

Superoxide dismutase (SOD)

A

breaks down powerful superoxide anions generated by aerobic respiration

46
Q

Catalase

A

converts hydrogen peroxide to water and oxygen

47
Q

Capnophiles

A

bacteria that grow best in a higher concentration of CO2 and a lower concetration of oxygen

48
Q

Candle jar

A

used to grow capnophiles

49
Q

Optimum growth pH

A

most favorable pH for growth of an organism

50
Q

Minimum growth pH

A

lowest pH value that an organism can tolerate

51
Q

Maximum growth pH

A

highest pH an organism can tolerate

52
Q

Neutrophiles

A

grow optimally as a pH within 1 or 2 pH units of the neutral pH of 7

53
Q

Acidophiles

A

microorganisms that grow optimally as a pH less than 5.55

54
Q

Alkaliphiles

A

microorganisms that grow best as a pH between 8.0 & 10.5

55
Q

Optimum growth temperature

A

best temperature for microorganism to grow at; growth rates are the highest at this temp

56
Q

Minimum growth temperature

A

lowest temp at which an organism can survive and replicate

57
Q

Maximum growth temperature

A

highest temp at which growth can occur

58
Q

Mesophiles

A

adapted to moderate temps, optimal growth temps ranging from 20 degrees C to 45 degrees C

59
Q

Pyschrotroph

A

also known as psychrotolerant, prefer cooler environments, from temp of 25 degrees C to 4 degrees C

60
Q

Psychrophiles

A

microorganisms that can grow at 0 degrees C and below, have optimum temp of 15 degrees C, don’t grow above 20 degrees C

61
Q

Thermophiles

A

organisms that grow at optimum temps of 50 degrees C to 80 degrees C

62
Q

Hyperthermophiles

A
63
Q

Halophiles

A
64
Q

Halotolerant

A
65
Q

Barophiles

A
66
Q

Enriched media

A
67
Q

Fastidious organisms

A
68
Q

Chemically defined medium

A
69
Q

Complex media

A
70
Q

Selective media

A
71
Q

Enrichment culture

A
72
Q

Differential media

A
73
Q

Cytokinesis

A

when the cell’s cytoplasm divides

74
Q

4 phases of the growth curve

A
  • lag phase
  • log phase
  • stationary phase
  • death phase
75
Q

1st stage of formation of a biofilm

A

involves attachment of planktonic cells to a surface coated with a substrate

76
Q

2nd stage of formation of a biofilm

A

attachment to substrate is reversible, cells express new phenotypes to facilitate EPS formation, transition from planktonic to sessile lifestyle

77
Q

3rd stage of formation of a biofilm

A

growth & cell division

78
Q

4th stage of formation of biofilm

A

biofilm develops characteristic structure

79
Q

5th & final stage of formation of a biofilm

A

cells on periphery of biofilm revert to planktonic lifestyle, sloughing off biofilm to colonize new sites

80
Q

obligate (strict) aerobes

A

can’t grow without an abundant supply of oxygen

81
Q

obligate anaerobes

A

killed by oxygen

82
Q

facultative anaerobes

A

thrive in presence of oxygen but can also grow in its absence by relying on fermentation or anaerobic respiration

83
Q

aerotolerant anaerobes

A

indifferent to presence of oxygen; don’t use oxygen because they usually have fermentative metabolism; aren’t harmed by presence of oxygen

84
Q

microaerophiles

A

bacteria that require a minimum level of oxygen for growth

84
Q

microaerophiles

A

bacteria that require a minimum level of oxygen for growth

microbiology (30 decks)

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