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Microbiology > Bacterial Visualization, Growth and Control > Flashcards

Bacterial Visualization, Growth and Control Flashcards

1
Q

resolution is more important than _____

A

magnification

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2
Q

stain increases ____________

A

contrast

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3
Q

contrast increases _______

A

resolution

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4
Q

visualizing bacteria depends on (3)

A

magnification, contrast, resolution

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5
Q

sample fixation (def)

A

secures sample to slide before staining
kills sample
eliminates movement

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6
Q

sample fixation types

A

heat fixation

chemical fixation

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7
Q

heat fixation

A

dry sample on slide, pass sample/ slide through flame

denatured proteins in sample adhere sample to slide

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8
Q

chemical fixation

A

less damaging that heat

use for delicate samples (flagella, formalin)

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9
Q

basic stain

A

most common
positive ion colored
binds negatively charged cell surface

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10
Q

acidic (negative) stain

A

negative ion colored
stain repelled from negatively charged cell surface
ink darkens background around cell to show cell shape, arrangement

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11
Q

basic stain examples

A

safranin, carbolfuschin, crystal violet, methylene blue, malachite green

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12
Q

acidic (negative) stain example

A

nigrisin

india ink

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13
Q

mordant

A

not a stain

iodine (negative ion, heat

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14
Q

mordant function

A

increases affinity for stain, enhancing cell staining

increases visibility of external cell walls, flagella

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15
Q

staining techniques (3)

A

vital
simple
differential

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16
Q

vital stain

A

stains living sample
adds color to wet mount and hanging drop preparations
no heat fixation

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17
Q

simple stain

A

1 stain
stains all cells same color
methylene blue, crystal violet

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18
Q

differential stain

A

distinguishes 2 different species in sample

2 stains

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19
Q

differential stain types (5)

A 
Gram stain
acid fast stain
endospore stain
capsule stain
flagella stain
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20
Q

4 steps to a differential stain

A
  1. primary stain- stains all species same color
  2. mordant
  3. destaining
  4. counterstain
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21
Q

Gram stain

A

distinguishes Gram positive bacteria (blue) from Gram negative (pink)

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22
Q

Gram stain steps

A

Start with heat fixed sample.
primary stain- crystal violet 1 min, rinse H20, mordant- iodine 1 min, rinse H20, Destain with acetone 5-10 seconds, rinse with water. Counterstain with safranin 3 min, rinse with water. Blot.

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23
Q

acid fast stain

A

stains Mycobacterium red

all others blue after counterstain

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24
Q

acid fast stain steps

A

primary stain carbolfucshin, heat slide to steaming (mordant) destain with alcohol- only Mycobacterium retain red. Counterstain with methylene blue.

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25
Q

endospore stain

A

stains endospores in their resistant stage, able to survive harsh conditions
ex Bacillus, Clostridium
endospores appear blue/green inside of pink cells

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26
Q

endospore stain steps

A

primary stain malachite green, heat (mordant) destain with water, counterstain with safranin

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27
Q

capsule stain

A

shows shape, arrangement of cells, thickness of capsule
ink is repelled from capsule surface so the cells appear white against black background
Klebsiella, Cryptococcus

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28
Q

capsule stain steps

A

primary stain India ink, counterstain methylene blue

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29
Q

flagella stain

A

requires gentle chemical fixation without heat

shows number and arrangement of flagella

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30
Q

pure culture

A

contains single species, not a mixture
derived from a single cell
colonies must not touch other colonies on plate to be certain culture is pure

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31
Q

3 techniques to obtain isolated colonies

A

streak plate
pour plate
spread plate

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32
Q

streak plate

A

easiest technique

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33
Q

pour plate

A

sample mixed in liquid agar

poured and allowed to harden

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34
Q

spread plate

A

sample poured on hardened agar

spread with sterile glass rod

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35
Q

culture media definition

A

solid or liquid containing nutrients or other agents required for growth

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36
Q

agar

A

polysaccharide from red algae

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37
Q

defined medium

A

known chemical composition

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38
Q

minimal defined medium

A

contains just enough nutrients to support growth

ex E. Coli mostly self-sufficient
Leuconostoc very demanding, requires many substances to grow

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39
Q

rich defined medium

A

excess nutrients

grows largest number of species

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40
Q

undefined (complex) medium

A

exact composition unknown, grows all species

contains: beef, blood, casein, yeast, soybeans

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41
Q

undefined medium examples

A

tryptic soy agar (TSA)

nutrient agar

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42
Q

selective medium

A

favors some species while inhibiting others
ex- salt agar isolates salt tolerant species from mixed sample
Staphylococcus

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43
Q

salt agar

A

isolates salt tolerant species from mixed sample

Staphylococcus

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44
Q

differential medium

A

growth characteristics on agar distinguish different species

ex- blood agar

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45
Q

blood agar

A

all species grow, colonies look different on blood

46
Q

beta hemolysis

A

complete breakdown of red blood cells

47
Q

alpha hemolysis

A

partial breakdown of red blood cells

48
Q

gamma hemolysis

A

no effect on red blood cells, no hemolysins

49
Q

mobility agar

A

all species grow

distinguished by movement in agar

50
Q

selective and differential agar

A

selects some, differentiates by appearance

51
Q

mannitol salt agar

A

selects for salt tolerant species
inhibits salt intolerant species
yellow color- Staphylococcus aureus

52
Q

MacConkey agar

A

selects for Gram positives, inhibits Gram negatives

differentiates colonies by lactose fermentation- pinkish to reddish color

53
Q

E. coli in MacConkey agar

A

ferments lactose

forms reddish colonies

54
Q

Shigella and Salmonella in MacConkey agar

A

do not ferment lactose

form white colonies

55
Q

enrichment procedure

A

expose mixed sample to unusual treatments

56
Q

endospore isolation

A

boil sample, only spore formers survive

57
Q

environmental conditions that directly influence bacterial growth

A

temperature, pH, oxygen

58
Q

temperature maintenance

A

incubators, water baths, refrigerators

59
Q

psychrophiles

A

cold tolerant bacteria

60
Q

mesophiles

A

room temperature loving bacteria

61
Q

thermophiles

A

heat tolerant bacteria

62
Q

E. coli optimum growth

A

37 C

proteins begin to denature at 40 C+

63
Q

pH

A

measure of hydrogen ions in solution

64
Q

fungi pH

65
Q

blood pH

A

7.4 (7.2 and 7.6 are toxic)

66
Q

buffers

A

prevent abrupt changes in pH
donate or remove Hydrogen ions in solutions
ex phosphate salts, calcium carbonate added to culture

67
Q

oxygen manipulation techniques (3)

A

thioglycolate
Brewer anaerobic jar
candle jar

68
Q

thioglycolate

A

establishes oxygen gradient in culture

bottom of tube anaerobic

69
Q

Brewer anaerobic jar

A

combines oxygen with hydrogen to form water

anaerobic

70
Q

candle jar

A

burning candle reduces oxygen concentration

microaerophilic

71
Q

strictly aerobic

A

require atmospheric levels of oxygen

Pseudomonas aeriginosa

72
Q

obligate anaerobic

A

do not use oxygen
killed by oxygen
Clostridium

73
Q

faculative anaerobic

A

use oxygen if present but can live without it
E. coli
Staphylococcus aureus

74
Q

aerotolerant anaerobic

A

do not use oxygen but not harmed by it

Lactobacillus

75
Q

microaerophiles

A

require oxygen but less than atmospheric
Neisseria sicca
Micrococcus

76
Q

Bacterial growth limiting factors

A

physical- temperature, pH, osmotic pressure
chemical- all molecules required for growth and reproduction
C, O, N, S, P, trace elements, organic growth factors

77
Q

bacterial growth curve phases

A

lag, log (exponential), stationary, death (decline)

78
Q

lag phase

A

onset of colony formation from 1 cell or few cells

length depends on inoculation source, amount of resources available

79
Q

log (exponential) phase

A

begins with few cells, optimal conditions and abundant resources
exponential growth characterized by rapid doubling time

80
Q

log phase limitations

A

environment changes as numbers increase
nutrients are depleted, pH changes (more acidic), toxins increase
growth rate declines, levels off

81
Q

stationary phase

A

population size remains constant
number of cells added equals number of cells dying
cell metabolism shifts from reproduction to survival
lasts indefinitely if minimum resource levels can be maintained

82
Q

carrying capacity

A

maximum number of individuals environment will support

83
Q

death (decline) phase

A

resources eventually become limited

existing cells die off at a faster rate than new cells are added

84
Q

targets of control treatments

A

external cell wall, cell membrane, proteins, nucleic acids (DNA, RNA), ribosomes, enzymes

85
Q

bacterial control methods

A

disinfection/ sterilization, physical/ chemical

86
Q

disinfection

A

microbiostatic- does not completely eliminate bacteria
inhibits or prevents growth- low numbers not disease causing
decontamination, antisepsis

87
Q

decontamination

A

remove bacteria from surfaces

88
Q

antisepsis

A

disinfection of living tissue

89
Q

sterilization

A

microbiocidal; kills all microbes including endospores

90
Q

physical controls

A 
heat
refrigeration
radiation
osmotic treatment
filtration
91
Q

heat treatments

A

moist heat
dry heat
flame sterilization
pasteurization

92
Q

moist heat

A

steam

autoclave

93
Q

dry heat

A

oven

less effective than moist heat

94
Q

flame sterilization

A

aseptic transfer of organisms

95
Q

pasteurization

A

briefly expose perishable fluids to high heat

96
Q

flash pasteurization

A

continuous, high temp, short time

milk 72C for 15 seconds- kills all pathogens

97
Q

continuous ultra high temp pasteurization

A

140 C for 1 to 3 seconds

may affect taste

98
Q

batch (vat) pasteurization

A

63C, 30 min

99
Q

superheated steam

A

sterilization
store liquids at room temperature without spoiling
product may degrade- dairy coffee creamer

100
Q

refrigeration

A

low temp does not kill but slows metabolism, reproduction

101
Q

radiation

A

damages DNA and denatures proteins

102
Q

radiation types

A

ionizing
non ionizing
microwaves

103
Q

ionizing radiation

A

high energy, penetrating, X rays, gamma rays

penetrates covers- food, medical supplies, mail

104
Q

non ionizing radiation

A

lower energy, non penetrating, uv light
does not penetrate covers- wrappers, surfaces
requires direct exposure to radiation

105
Q

microwaves

A

less effective than bacteria

longer wavelength, lower energy

106
Q

osmotic treatment

A

high solute concentration (salt, sugar)

create hypertonic environment to remove water from cells but do not kill cells

107
Q

filtration

A

filters remove most bacteria- does not remove viruses

sterilize liquids or gases damaged by heat

108
Q

chemical treatments

A

kills bacteria or reduces numbers to low levels

109
Q

chemical treatment examples

A

bleach- kill bacteria on slides; pipettes
lysol- clean bench
isopropanol- kills bacteria, cleans surface, evaporates quickly
soap- emulsifies lipids, helps remove bacteria from surfaces
ethylene oxide (gas)- deeply penetrating, requires more time; used to sterilize space craft returning from moon and Mars, sterilize medical equipment

110
Q

effectiveness of control treatments depends on

A
  • characteristics of organism being treated
  • number of cells in colony and growth stage colony is in
  • organic substances in environment may interfere with treatments
  • temperature and length of exposure time
111
Q

D-value

A

decimal reduction time
measures rate of decline in response to heat treatment
time in minutes required to kill 90% of population at given temperature
90% die in 10 minutes- 90% of remaining 10% die in next 10 minutes

112
Q

Microbial death graph

A

higher temp, shorter time

Microbiology (27 decks)

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