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MICROBIOLOGY Midterm#1 > CH. 6: Microbial Growth > Flashcards

CH. 6: Microbial Growth Flashcards

1
Q

growth

A

increase in numbers of cells, not size

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2
Q

colonies

A

hundreds of thousands of cells

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3
Q

population

A

growth to billions of cells

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4
Q

knowledge of microbial growth needed to

A

control growth of pathogenic microbes and increase growth of good microbes as well as those we want to study

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5
Q

physical requirements for growth

A

temp
pH
osmotic pressure

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6
Q

chemical requirements for growth

A 
carbon
N, S, P
trace elements
oxygen
organic growth factor
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7
Q

most bacteria will grow at (temp)

A

37C

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8
Q

minimum growth temp

A

lowest temperature at which there will be some growth

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9
Q

optimum growth temp

A

usually closer to the max end of the temp range; best growth conditions

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10
Q

maximum growth temp

A

highest temp at which growth is possible

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11
Q

growth temperature ranges span

A

30C

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12
Q

3 primary groups of microbe classification based on preferred temp range

A
  1. psychrophiles
  2. mesophiles
  3. thermophiles
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13
Q

psychrophiles grow at

A

0C and optimum 15C

usually no growth at 25C

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14
Q

psychrophiles grow where?

A

ocean depths, and polar regions

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15
Q

psychrotophs grow at

A

[classification not as strict]
0C (same as psychrophiles)
optimum between 20-30C (when psychrophiles will die)
not at temps above 40C
more common than psychrophiles & these cause food spoilage

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16
Q

mesophiles

A

– most common type of microbe
optimum growth between 25-40C
– the mesophiles include most of the common spoilage and disease organisms

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17
Q

thermophiles grow at

A

optimum 50-60C (T for hot water tap)
many do not grow below 40C
important in organic compost piles

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18
Q

hyperthermophile archaea grow at

A

80C or higher

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19
Q

hyperthermophiles found where

A

hydrothermal vents (ie. deep sea vents)

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20
Q

hyperthermophiles useful bacteria in

A

biotechnology (e.g. deep vent DNA polymerase or PCR)
Tli has proofreading capability
Taq does NOT

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21
Q

most bacteria grow b/w pH of

A

6.5-7.5 (near neurtrality)

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22
Q

foods fermented preserved via acidity bc

A

very few bacteria like acidic conditions

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23
Q

acidophiles

A

grow in acidic environments

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24
Q

molds and yeasts grow between pH of

A

5-6 (acidic)

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25
Q

bacterial cultures produce ______ that inhibit their growth: ______ are included in media to counter this

A

acids

buffers

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26
Q

hypertonic environments (or an increase in salt or sugar) cause

A

plasmolysis (shrinkage of cytoplasm)

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27
Q

most bacteria grow in media that is

A

mostly water

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28
Q

agar

A

a complex polysaccharide used to solidify media constitutes only 1/5%
(increasing agar concentration can cause plasmolysis and inhibit bacterial growth)

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29
Q

extreme or OBLIGATE halophiles (archaea)

A

require HIGH osmotic pressure (salty water)

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30
Q

facultative halophiles

A

do not require but can tolerate high osmotic pressure

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31
Q

carbon…

A

maintains structural organic molecules
is an energy source
important requirement for bacterial growth (besides water)

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32
Q

[carbon] chemoheterotrophs..

A

use organic carbon sources
–> organisms that derive energy by ingesting intermediates or building blocks that they are incapable of producing on their own

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33
Q

[carbon] autotrophs…

A

use CO2

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34
Q

half of dry weight of bacteria is

A

carbon

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35
Q

nitrogen…

A

for anabolic processes ie. synthesis of amino acids (for proteins), DNA and RNA

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36
Q

14% of dry weight of bacteria is

A

nitrogen

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37
Q

nitrogen obtained from

A
    • protein-containing matter - decomposition of proteins
    • NH4+ in organic matter or NO3-
    • a few (photosynthesizing) bacteria use N2 via NITROGEN FIXATION
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38
Q

example of bacteria that uses nitrogen fixation

A

Rhizobium

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39
Q

sulfur…

A

used to make amino acids and vitamins (thiamine and biotin)

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40
Q

sources of sulfur

A

decomposition of sulfur-containing proteins

some bacteria use SO4(2-) or H2S

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41
Q

phosphorus…

A

in DNA, RNA, ATP, and membranes (phospholipids)

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42
Q

phosphorus source

A

PO4(3-)

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43
Q

4% of dry weight of bacteria is

A

P and S together

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44
Q

trace elements

A

inorganic elements required in small amounts
usually as enzyme cofactors
ie. iron, copper, molybdenum, zinc
* tap water is the source

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45
Q

microbes also use _____ as cofactors

A

potassium, magnesium, and calcium

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46
Q

oxygen…

A

required for aerobic respiration but can be toxic

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47
Q

obligate aerobes =

A

only aerobic growth, O2 required

48
Q

obligate aerobes grow (test tube)

A

at the top, where high O2 concentrations have diffused into medium

49
Q

facultative anaerobes =

A

both aerobic and anaerobic growth

greater growth in presence of oxygen

50
Q

facultative anaerobes (test tube)

A

most growth at top (where MOST O2 is present); but growth occurs throughout the tube as well

51
Q

obligate anaerobes =

A

only anaerobic growth; growth stops in presence of O2

52
Q

obligate anaerobes (test tube)

A

growth only occurs at the bottom of the tube where there is no oxygen.

53
Q

aerotolerant anaerobes =

A

only anaerobic growth, but continues in presence of oxygen

54
Q

aerotolerant anaerobes (test tube)

A

growth occurs evenly throughout, O2 has no effect

55
Q

microaerophiles =

A

obly aerobic growth; O2 required in LOW CONCENTRATION

56
Q

microaerophiles growth (test tube)

A

in the middle of the medium, not near bottom where no O2, not near top where lots of O2 diffused into medium.

57
Q

toxic oxygen

A

singlet oxygen
superoxide free radicals
peroxide anion
hydroxyl radical

58
Q

singlet oxygen

A

1O2-

–> boosted to a higher energy state than O2 and is extremely reactive

59
Q

superoxide free radicals

A

O2 w/ funny dot/line superscript

  • -> are formed in small amounts during the normal respiration of organisms that use oxygen as a final electron acceptor, forming water.
  • -> Their toxicity is caused by their great instability, which leads them to steal an electron from a neighboring molecule, which in turn becomes a radical and steals an electron, and so on.
60
Q

peroxide anion

A

O2(2-) (from H2O2)
–> Because the hydrogen peroxide produced during
normal aerobic respiration is toxic, microbes have developed enzymes to neutralize it. The most familiar of these is catalase, which converts it into water and oxygen.
–> The other enzyme that breaks down hydrogen peroxide is peroxidase, which differs from catalase in that its reaction does not produce oxygen.

61
Q

hydroxyl radical

A

OH with funny little dot

    • transient
    • The hydroxyl radical (OH·) is another intermediate form of oxygen and probably the most reactive. It is formed in the cellular cytoplasm by ionizing radiation. Most aerobic respiration produces traces of hydroxyl radicals, but they are transient.
62
Q

macrophage phagolysosome

A

after ingestion of microbe by phagocyte, there is formation of a phagosome.

  • -> then FUSION OF THE PHAGOSOME WITH A LYSOSOME to form a phagolysosome
  • -> then digestion of ingested microbe by enzymes
63
Q

organic growth factors

A

organic growth compounds obtained from the environment

ie. vitamins, amino acids, purines, pyrimidines

64
Q

biofilms

A

microbial communities in nature; share nutrients; sheltered from environmental harm (dessication, antibiotics, immune system)

65
Q

another name for biofilm

A

hydrogel

66
Q

biofilm matrix composed of

A

polysaccharide (glycocalyx), DNA and proteins sometimes called slime

67
Q

quorum sensing

A

cell-to-cell communication that occurs in biofilms

68
Q

conjugation in biofilms:

A

transfers genes like antibiotic resistance

69
Q

structures in biofilms

A

pillar like (allows water flow to bring nutrients and remove waste)

70
Q

biofilms formed when

A

a plantonic (free-living) cell adheres to a surface

    • can also form floc in sewage or streamers in running water
    • catheter example: pts with indwellings recieved contaminated heparin; bacterial numbers in heparin too low to cause infection; but 84-421 days after exposure, pts developed infections
71
Q

medical relevance of biofilms

A
  • microbes in films are very resistance to microbicides
  • cause most (70%) of human bacterial infections
  • cause most nosocomial infections (catheters, heart valves)
  • infections from contact lenses, dental caries
72
Q

prevention of biofilms

A
  • treat surfaces with antimicrobials
  • interrupt quorum sensing pathways
  • inhibit surface mobility essential for biofilm formation (ie. lactoferrin binds iron and inhibits surface mobility reducing pseudomonad biofilm formation in cystic fibrosis)
73
Q

culture medium:

A

nutrients prepared for microbial growth; must meet nutritional requirements, be at correct pH and moisture levels, be sterile, and incubated at correct temp

74
Q

inoculum:

A

introduction of microbes into medium

75
Q

culture:

A

microbes growing in/on culture medium

76
Q

agar

A

complex polysaccharide from maine algae

  • used as solidifying agent for culture media in petri plates/slants/deeps
    • generally NOT METABOLIZED by microbes (metabolites are added to it)
77
Q

agar liquifies at

A

100C

78
Q

agar solidifies at

A

40C

79
Q

chemically defined media:

A

exact chemical composition is known

80
Q

complex media:

A

extracts and digests of yeasts, meat, or plants

    • energy requirements primarily in form of protein
    • nutrient broth
    • nutrient agar
81
Q

[anaerobic culture methods]

reducing media:

A

contain chemicals (thioglycolate or oxyrase) that combine with O2

  • placed in tightly capped tubes
  • heated to drive off O2 before use
82
Q

capnophiles

A

microbes that require high CO2 concentrations
- prefer conditions similar to our intestines, resp tract, and other internal body tissues
- special culturing techniques
(CO2 packet, candle jar, CO2 incubators)

83
Q

biosafety level 1

A

no special precautions

84
Q

biosafety level 2

A

lab coat, gloves, eye/face protection

85
Q

biosafety level 3

A

biosafety cabinets to prevent airborne transmission

86
Q

biosafety level 4

A

sealed, negative pressure- air goes in (exhaust air HEPA filtered twice, separate air supply and suits for personnel)

87
Q

differential media:

A

make it easy to distinguish colonies of different microbes (ie. blood agar)

88
Q

selective media:

A

suppress unwanted microbes and encourage desired microbes (ie. mannitol-salt agar)

89
Q

enrichment culture:

A

encourages growth of desired microbe

90
Q

a pure culture:

A

contains only one species or strain

91
Q

a colony:

A

is a population of cells arising from a single cell or spore or grom a group of attached cells

92
Q

the streak plate method:

A

is used to isolate pure cultures

93
Q

only _% of bacteria in ecosystem can be cultured

A

1%

94
Q

3 examples of obligate intracellular pathogens:

A
  • Mycobacterium leprae
  • Treponema pallidum
  • Chlamydia spp
95
Q

preserving bacterial cultures short-term

A

refrigeration

96
Q

deep-freezing

A

preserving bacterial cultures

-50 to -95C

97
Q

lyophilization

A

freeze-drying

frozen (-54 to -72C) and dehydrated in a vacuum

98
Q

reproduction in prokaryotes (4)

A
    • binary fission
    • budding
    • conidiospores (actinomycetes) [filamentous bacteria - at tips of filaments)
    • fragmentation of filaments
99
Q

generation time

A

the time required for the population to double (log formula/0.301)

100
Q

generation time formula

A

60 min x hours / number of generations = ____ mins/generation

101
Q

[bacterial growth curve]

LAG phase

A

intense activity preparing for population growth but no increase in population.

102
Q

[bacterial growth curve]

LOG phase

A

logarithmic, or exponential, increase in population (is due to reproduction by binary fission in bacteria or mitosis in yeast)

103
Q

[bacterial growth curve]

STATIONARY phase

A

period of equilibrium: microbial deaths balance production of new cells

104
Q

[bacterial growth curve]

DEATH phase

A

population is decreasing at a logarithmic rate

105
Q

plate counts

A
    • measures number of viable cells
    • done by pour plate or spread plate method
    • takes time (>24h)
    • after incubation, count colonies on plates that have 25-250 colonies (CFUs)
106
Q

numbers in plate counts reported as

A

CFUs (in a given volume or mass)

107
Q

what helps ensure accuracy in plate counts?

A

performing serial dilutions

108
Q

most probably number

A

multiple tube MPN test

    • count positive tubes
    • useful for organisms that do not grow on a solid medium
    • 95% statistical probability that the number falls within a given range
    • compare with statistical table
109
Q

direct microscopic count

A
    • sample injected onto slide and stained
    • sample is viewed under high magnefication
    • DIFFICULT TO USE w/ MOTILE BACTERIA
    • DEAD CELLS will be included
    • HIGH SAMPLE CONCENTRATION required
    • VERY FAST
110
Q

direct microscopic count formula

A

number of bacteria/ml =

number of cells counted / volume of area counted

111
Q

turbidity

A

using light, a bacterial suspension (test tube), and a spectophotometer with a light-sensitive detector

    • HIGH CONCENTRATION OF BACTERIA required
    • 10-100 million cells/ml
112
Q

metabolic activity

A

measures a microbial product (ie. if they secrete a certain product/chemical etc).
- used in assays (e.g. studying effects of pressure on microbial activity)

113
Q

metabolic activity assumes

A

amount of product is proportional to number of bacteria

114
Q

dry weight

A

useful for filamentous bacteria or molds

filamentous bacteria and spread plates do not work

115
Q

[measuring microbial growth]

DIRECT methods

A
  1. plate counts
  2. filtration
  3. MPN
  4. direct microscopic count
116
Q

[measuring microbial growth]

INDIRECT methods

A
  1. turbidity
  2. metabolic activity
  3. dry weight

MICROBIOLOGY Midterm#1 (4 decks)

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