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microbio > lecture 3 > Flashcards

lecture 3 Flashcards

1
Q

prokaryotic cells divide by

A

binary fission

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2
Q

population doubles each division

A

exponential growth

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3
Q

the time it takes for the population to double

A

generation time

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4
Q

generation time varies on

A

the species and environmental conditions

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5
Q

what is microbial growth defined as

A

an increase in the number of cells in a population

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6
Q

what is the equation for prokaryotic growth calculation

A

N1=N0x2^n

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7
Q

what does N1 mean in the microbial growth calculation

A

number of cells in population at time t

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8
Q

what does N0 mean in the microbial growth calculation

A

initial number of cells

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9
Q

what does n mean in the microbial growth calculation

A

number of generations at that point

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10
Q

rapid generation time with optimal conditions can yield _____

A

huge populations quickly

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11
Q

in nature, microbial growth usually live in

A

polymer-encased communities termed biofilms

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12
Q

what do biofilms cause?

A

slipperiness of rocks in stream bed, slimy gunk in sink drains, dental plaque

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13
Q

in biofilm formation, free cells _____

A

adhere to surface and multiply

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14
Q

in biofilm formation, after free cells multiply, what happens next?

A

the cells release polymers to which unrelated cells may attach and grow

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15
Q

what gives a slimy appearance in biofilms

A

extra polymeric substances (EPS)

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16
Q

where do nutrients and wastes pass through in biofilms?

A

characteristic channels

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17
Q

in biofilms, cells communicate with one another via ______

A

chemical signals

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18
Q

biofilms have important implications, such as _____

A

dental plaque leading to tooth decay,
most infections seem to involve biofilms,
accumulation in pipes, drains (can be hundreds of times more resistant to disinfectants)

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19
Q

biofilms can also be helpful, in cases such as _____

A

bioremediation, wastewater treatment

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20
Q

microbes within biofilms are often resistant to _______

A

immune system and antibiotics

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21
Q

microorganisms regularly grow in close association with ______

A

many different species

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22
Q

microorganism interactions with different species can _____

A

foster growth of species otherwise unable to survive
(for example: strict anaerobes can grow in mouth if others consume O2, metabolic waste of one can serve as a nutrient for other)

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23
Q

the interactions between microorganisms and different species can often be ______

A

competitive

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24
Q

how do some gram-negative bacteria deal with competitors?

A

use needle-like structure called a type VI secretion system to inject toxic compounds directly into competing bacteria

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25
Q

to inhibit competitors, some microorganisms _____

A

synthesize toxic compounds

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26
Q

population of cells derived from a single cell; allows study of a single species

A

pure culture

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27
Q

in pure cultures, organisms may _____

A

behave differently than in nature

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28
Q

what percent of microorganisms can be cultured?

A

1%

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29
Q

pure culture obtained (and maintained) using _____

A

aseptic technique

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30
Q

aseptic techniques minimize ____

A

accidental introduction of other organisms

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31
Q

cells grow in or on culture medium contain

A

nutrients dissolved in water

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32
Q

cells grow in or on culture medium can be

A

liquid broth or solid gel

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33
Q

what do you need to obtain a pure culture?

A

culture medium, container, aseptic conditions, method to separate individual cells

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34
Q

what happens in correct conditions when a pure culture is obtained?

A

a single cell will multiply to form a visible colony (approximately 1 million cells easily visible)

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35
Q

what is used to solidify a medium in a pure culture

A

agar

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36
Q

why is agar a good solidifier for the medium

A

it’s not destroyed by high temperatures and can be sterilized
solid over temperature range for most microbial growth
degraded by only very few microbes

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37
Q

a pure culture is grow in a

A

petri dish

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38
Q

petri dish with agar nutrient medium

A

agar plate

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39
Q

two-part covered container of glass or plastic
allows air to enter, but excludes contaminants

A

petri dish characteristics

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40
Q

simplest, most commonly used method for isolating in obtaining a pure culture

A

streak-plate method

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41
Q

what does the streak-plate method do?

A

reduces number of cells with each series of streaks

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42
Q

what do separated cells do in the streak-plate method?

A

form distinct, isolated colonies

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43
Q

a pure culture can be maintained as a ______

A

stock culture

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44
Q

what is a stock culture often stored as?

A

agar slant

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45
Q

cells can be frozen at ______ for long-term storage

A

-70 degrees celsius

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46
Q

what are cells mixed with for long term storage?

A

glycerol to prevent ice crystal formation

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47
Q

stock cultures can be ____ for storage

A

freeze-dried

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48
Q

culture in which nutrients are not added, nor are wastes removed

A

closed system

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49
Q

closed systems are also called

A

batch cultures

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50
Q

closed systems include

A

microorganisms grown on agar plates or in tubes or flasks of broth

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51
Q

what is seen in closed broth culture?

A

characteristic growth curve

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52
Q

number of cells does not increase
cells begin synthesizing enzymes required for growth
delay depends on conditions

A

lag phase

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53
Q

at which stage do cells divide at a constant rate?

A

exponential (log) phase

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54
Q

what happens when cells are dividing at a constant rate?

A

generation time measured,
most sensitive to antibiotics

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55
Q

what is formed during the exponential (log) phase?

A

primary metabolites, secondary metabolites

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56
Q

example of primary metabolites

A

amino acids

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57
Q

what are secondary metabolites produced as?

A

secondary metabolites such as antibodies are produced as nutrients and depleted, leading to waste accumulation

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58
Q

phases of the growth curve

A

lag phase
exponential (log) phase
stationary phase
death phase
phase of prolonged decline

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59
Q

nutrient levels too low to sustain growth
total number remain constant

A

stationary phase

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60
Q

in the stationary phase, what occurs?

A

some cells die, releasing nutrients; others grow

continue to produce secondary metabolites

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61
Q

total number of viable cells decreases

A

death phase

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62
Q

what happens in the death phase?

A

cells die at constant rate
exponential, but usually much slower than cell growth

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63
Q

phase of prolonged decline

A

some fraction may survive, and they are adapted to tolerate worsened conditions

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64
Q

growth of bacteria on solid medium and liquid broth is similar, but ______

A

there are important differences

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65
Q

____ of single cell in a colony determines its environment

A

position

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66
Q

edge of colony

A

little competition for O2, nutrients

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67
Q

center of colony

A

depleted O2, nutrients
accumulation of potentially toxic wastes

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68
Q

cells at edges of colony may show ______ while those in the center are in the ______

A

exponential growth, death phase

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69
Q

culture to which nutrients are continually added and waste products removed

A

open system

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70
Q

provides an open system that can maintain continuous growth

A

chemostat

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71
Q

in a chemostat, ______ and ______ can be controlled to achieve constant growth rate and cell density

A

nutrient content, speed of addition

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72
Q

a chemostat produces ______

A

relatively uniform population to study response to different conditions

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73
Q

a chemostat can maintain cells in _____

A

log phase of growth to harvest commercially valuable products

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74
Q

as a group, microorganisms inhabit _____

A

nearly all environments

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75
Q

extremophiles live in

A

harsh environments

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76
Q

most extremophiles are

A

archaea

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77
Q

major factors that affect microbial growth

A

temperature
atmosphere
pH
water availability

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78
Q

environmental factors that influence microbial growth

A

temperature
oxygen availability
pH
water availability

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79
Q

types of temperature as an environmental factor

A

psychrophile
psychrotroph
mesophile
thermophile
hyperthermophile

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80
Q

types of oxygen availability as an environmental factor

A

obligate aerobe
facultative anaerobe
obligate anaerobe
microaerophile
aerotolerant anaerobe

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81
Q

types of pH as an environmental factor

A

neutrophile
acidophile
alkalophile

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82
Q

types of water availability as an environmental factor

A

halotolerant
halophile

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83
Q

thermostability appears to be due to protein structure

A

temperature

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84
Q

optimum temperature between -5 degrees celsius and 15 degrees celsius

A

psychrophile

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85
Q

optimum temperature between 15 degrees celsius and 30 degrees celsius, but grows well at refrigeration temperatures

A

psychrotroph

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86
Q

optimum temperature between 25 degrees celsius and 45 degrees celsius

A

mesophile

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87
Q

optimum temperature between 45 degrees celsius and 70 degrees celsius

A

thermophile

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88
Q

optimum temperature of 70 degrees celsius or greater

A

hyperthermophile

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89
Q

oxygen requirement/tolerance reflects the organisms’s energy harvesting mechanisms and its ability to inactivate reactive oxygen species

A

oxygen availability

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90
Q

requires O2

A

obligate aerobe

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91
Q

grows best if O2 is present, but can also grow without it

A

facultative anaerobe

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92
Q

cannot grow in the presence of O2

A

obligate anaerobe

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93
Q

requires small amounts of O2, but higher concentrations are inhibitory

A

microaerophile

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94
Q

indifferent to O2

A

aerotolerant anaerobe (obligate fermenter)

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95
Q

prokaryotes that live in pH extremes maintain a near-neutral internal pH by ________

A

pumping protons out of or into the cell

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96
Q

multiplies in the range of pH 5 to 8

A

neutrophile

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97
Q

grows optimally at a pH below 5.5

A

acidophile

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98
Q

grows optimally at a pH above 8.5

A

alkalophile

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99
Q

prokaryotes that can grow in high-solute solutions maintain the availability of water in the cell by ______

A

increasing their internal solute concentration

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100
Q

can grow in relatively high-salt solutions, up to approximately 10% NaCl

A

halotolerant

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101
Q

requires high levels of sodium chloride

A

halophile

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102
Q

where are psychrophiles found?

A

in arctic and antarctic regions

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103
Q

what are psychotrophs important in?

A

spoilage of refrigerated foods

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104
Q

mesophile pathogens live in _____

A

35 degrees to 40 degrees celsius

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105
Q

thermophiles are common in _____

A

hot springs and compost heaps

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106
Q

hyperthermophiles are usually _____

A

archaea

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107
Q

hyperthermophiles are found in _____

A

hydrothermal vents

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108
Q

solidified agar slows _____

A

gas diffusion

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109
Q

top of shake tube is _____

A

aerobic

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110
Q

bottom of shake tube is _____

A

anaerobic

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111
Q

steps of measuring in shake tube

A

1) boil nutrient agar to drive off O2
2) cool to just above solidifying temperature
3) add microorganisms
4) gently swirl

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112
Q

requires O2 for respiration

A

obligate aerobe

113
Q

uses O2 for respiration, if available

A

facultative anaerobe

114
Q

does not use O2 for respiration

A

obligate anaerobe

115
Q

requires O2 for respiration

A

microaerophile

116
Q

does not use O2 for respiration (2)

A

aerotolerant anaerobe

117
Q

produces superoxide dismutase and catalase to protect against reactive oxygen species

A

obligate aerobe

118
Q

produces superoxide dismutase and catalase to protect against reactive oxygen species (2)

A

facultative anaerobe

119
Q

does not produce superoxide dismutase or catalase to protect against reactive oxygen species

A

obligate anaerobe

120
Q

produces some superoxide dismutase and catalase to protect against reactive oxygen species

A

microaerophile

121
Q

produces superoxide dismutase but not catalase to protect against reactive oxygen species

A

aerotolerant anaerobe

122
Q

bacterial growth at the top of test tube

A

obligate aerobe

123
Q

grows throughout test tube, but most growth is at the top of tube

A

facultative anaerobe

124
Q

grows at the bottom of the test tube

A

obligate anaerobe

125
Q

grows near the top of the test tube, but not all the way at the top

A

microaerophile

126
Q

grows equally throughout the test tube

A

aerotolerant anaerobe

127
Q

harmful by-products of using O2 in aerobic respiration

A

reactive oxygen species (ROS)

128
Q

reactive oxygen species include

A

superoxide and hydrogen peroxide

129
Q

reactive oxygen species are damaging to ____

A

cellular components

130
Q

cells must have ____

A

protective mechanisms

131
Q

obligate anaerobes typically do not have _____

A

protective mechanisms

132
Q

almost all organisms growing in presence of oxygen produce ______

A

enzyme superoxide dismutase

133
Q

superoxide dismutase inactivates ______

A

superoxide

134
Q

how does superoxide dismutase inactivate superoxide?

A

by converting it to O2 and H2O2

135
Q

almost all organisms also produce _____

A

catalase

136
Q

catalase converts _____

A

H2O2 to O2 and H2O

137
Q

what does not produce catalase?

A

aerotolerant anaerobes (makes for useful test)

138
Q

bacteria survive a range of pH, but they have _____

A

an optimum

139
Q

most bacteria maintain constant internal pH, which is typically _____

A

near neutral

140
Q

bacteria pump out protons if in ____

A

acidic environment

141
Q

bacteria bring in protons if in ______

A

alkaline environment

142
Q

what is the optimum of a neutrophile?

A

near pH 7

143
Q

most microbes are _____

A

neutrophiles

144
Q

food can be preserved by ______

A

increasing acidity

145
Q

where does H. pylori grow?

A

stomach

146
Q

what does H. pylori produce?

A

urease

147
Q

H. plyori produces urease to _____

A

split urea into CO2 and ammonia to decrease acidity of surroundings

148
Q

what has optimum pH of less than 1

A

picrophilus oshimae

149
Q

all microorganisms require _____ for growth

A

water

150
Q

what makes water unavailable to cell?

A

dissolved salts, sugars

151
Q

if solute concentration is higher outside of cell, water ______

A

diffuses out

152
Q

what is used to preserve food?

A

salt, sugar

153
Q

some microbes withstand or even require

A

high salt

154
Q

example of halotolerant

A

staphylococcus on dry salty skin

155
Q

marine bacteria is a _____

A

halophile, requires approximately 3 % salt

156
Q

extreme halophiles require

A

> 9 % (dead sea, utah’s salt flats)

157
Q

_____ required to synthesize cell components

A

nutrients

158
Q

major elements

A

carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, magnesium, calcium, and iron

159
Q

trace elements

A

cobalt, zinc, copper, molybdenum, manganese

160
Q

prokaryotes can use diverse sources to _____

A

acquire various elements

161
Q

component of amino acids, lipids, nucleic acids, and sugars

A

carbon, oxygen, and hydrogen

162
Q

component of amino acids and nucleic acids

A

nitrogen

163
Q

component of some amino acids

A

sulfur

164
Q

component of nucleic acids, membrane lipids, and ATP

A

phosphorus

165
Q

required for the functioning of certain enzymes; additional functions as well

A

potassium, magnesium, and calcium

166
Q

part of certain enzymes

A

iron

167
Q

carbon source distinguishes

A

different groups

168
Q

uses organic carbon

A

heterotrophs

169
Q

use inorganic carbon as CO2

A

autotrophs

170
Q

converts inorganic carbon to organic form

A

carbon fixation

171
Q

_____ required for amino acids, nucleic acids

A

nitrogen

172
Q

converting N2 gas to ammonia and then incorporating it into organic compounds

A

nitrogen fixation

173
Q

most organisms use ______

A

ammonia or aminonitrogen (some convert nitrate to ammonia)

174
Q

______ are often limiting nutrients

A

phosphorus and iron

175
Q

limiting nutrients available at

A

lowest concentrations relative to need

176
Q

limiting nutrients dictate

A

maximum level of microbial growth

177
Q

organic molecules that an organism cannot synthesize; must be present in the environment

A

growth factors

178
Q

growth factor requirements reflect

A

biosynthetic capabilities

179
Q

Most ______ synthesize all cellular components from glucose; no growth factors needed

A

E. Coli

180
Q

Neisseria species are _____

A

fastidious (they require numerous growth factors, including vitamins and amino acids)

181
Q

fastidious species can be used to ____

A

measure the quantity of vitamins in food products

182
Q

energy sources

A

sunlight, chemical compounds

183
Q

obtain energy from sunlight

A

phototrophs

184
Q

example of phototrophs

A

plants, algae, photosynthetic bacteria

185
Q

extract energy from chemicals

A

chemotrophs

186
Q

what extract energy from organic molecules?

A

mammalian cells, fungi, many types of prokaryotes

187
Q

common sources of organic molecules

A

sugars, amino acids, fatty acids

188
Q

some prokaryotes extract energy from _____

A

inorganic chemicals

189
Q

examples of inorganic chemicals

A

hydrogen sulfide, hydrogen gas

190
Q

energy from sunlight; carbon from CO2

A

photoautotrophs

191
Q

energy from sunlight; carbon from organic compounds

A

photoheterotrophs

192
Q

energy from inorganic compounds; carbon from CO2

A

chemolithoautotrophs

193
Q

what are chemolithoautotrophs also termed as

A

chemoautotrophs, chemolithotrophs

194
Q

energy and carbon from organic compounds

A

chemoorganoheterotrophs

195
Q

chemoorganoheterotrophs are also termed as

A

chemoheterotrophs, chemoorganotrophs

196
Q

contain a variety of ingredients

A

complex media

197
Q

the exact composition of complex media is _____

A

highly variable

198
Q

composed of exact amounts of pure chemicals

A

chemically defined media

199
Q

chemically defined media exhibit typically _____

A

slower growth as cells must synthesize components

200
Q

complex medium used routinely in clinical labs. differential because colonies of hemolytic organisms are surrounded by a zone of red blood cell clearing.

A

blood agar

201
Q

complex medium used to culture fastidious bacteria, particularly those found in clinical specimens.

A

chocolate agar

202
Q

blood agar is

A

not selective

203
Q

chocolate agar is

A

not selective or differential

204
Q

chemically defined medium. used in laboratory experiments to study nutritional requirements of bacteria

A

glucosesalts agar

205
Q

glucosesalts agar are

A

not selective or differential

206
Q

complex medium used to isolate gram-negative rods that typically reside in the intestine

A

MacConkey agar

207
Q

MacConkey agar is selective because

A

bile salts and dyes inhibit Gram-positive organisms and Gram-negative cocci

208
Q

MacConkey agar is differential because

A

the pH indicator turns pink-red when the sugar in the medium, lactose, is fermented

209
Q

nutrient agar is

A

not selective or differential

210
Q

complex medium used for routine labratory work. supports the growth of a variety of nonfastidious bacteria

A

nutrient agar

211
Q

ThayerMartin agar is not

A

differential

212
Q

ThayerMartin agar is selective because

A

it contains antibiotics that inhibit most organisms except Neisseria species

213
Q

complex medium used to isolate neisseria species, which are fastidious

A

ThayerMartin agar

214
Q

E. coli can grow in ____

A

complex media or chemically defined media

215
Q

nutrient broth is also known as

A

complex medium

216
Q

glucose-salts broth is also known as

A

chemically defined medium

217
Q

peptone is the complex medium, what is the chemically defined medium?

A

glucose

218
Q

beef extract is the complex medium, what is the chemically defined medium?

A

dipotassium phosphate

219
Q

water is the complex medium, what is the chemically defined medium?

A

monopotassium phosphate
magnesium sulfate
ammonium sulfate
calcium chloride
iron sulfate
water

220
Q

inhibit growth of certain species in a mixed sample, while allowing growth of species of interest

A

selective media

221
Q

MacConkey agar is selective for

A

Gram-negative rods

222
Q

MacConkey agar is differential for

A

lactose fermentation

223
Q

MacConkey agar contains

A

crystal violet that inhibits Gram-positive bacteria and bile salts that inhibit most non-intestinal bacteria

224
Q

contain substance that microbes change in identifiable way

A

differential media

225
Q

beta hemolysis of blood agar produces

A

clear zone

226
Q

alpha hemolysis of blood agar produces

A

zone of greenish partial clearing

227
Q

selective or differential media can be used to

A

detect or isolate a species from a mixed population

228
Q

most obligate aerobes and facultative anaerobes can be incubated in _____

A

air (approximately 20% O2)

229
Q

broth cultures are shaken to ____

A

provide maximum aeration

230
Q

many medically important bacteria (for example, Neisseria, Hemophilus) grow best with ____

A

increased CO2

231
Q

one method to increase CO2 is to

A

incubate in candle jar

232
Q

capnophiles

A

meaning requires increased CO2

233
Q

require lower O2 concentrations than achieved by candle jar

A

microaerophilic

234
Q

microaerophiles can incubate in

A

gas-tight container with chemical packet
(chemical reaction reduces O2 to 5 to 15%)

235
Q

obligate anaerobes sensitive to O2 are

A

anaerobic

236
Q

anaerobe containers are useful if

A

microbe can tolerate brief O2 exposures (can also use semisolid culture medium containing reducing agent such as sodium thioglycolate)

237
Q

reducing agents in anaerobe containers can reduce ____

A

O2 to water

238
Q

anaerobic chamber provides

A

more stringent approach

239
Q

used to isolate organism present as only a small fraction of mixed population

A

enrichment culture

240
Q

enrichment cultures provide

A

conditions promoting growth of particular species

241
Q

in an enrichment culture, the _______ increases

A

relative concentration of target organism

242
Q

direct cell counts find ______

A

total numbers of cells (living plus dead)

243
Q

cell-counting instruments

A

coulter counter
flow cytometer

244
Q

direct cell counts can be found with ____

A

direct microscopic count

245
Q

viable cell counts find ____

A

cells capable of multiplying, the number of microorganisms capable of growing in a given set of conditions

246
Q

viable cell counts can use _____

A

selective, differential media for particular species (can determine the number of specific microbial species)

247
Q

single cell gives rise to colony

A

plate counts

248
Q

number of colonies in a plate count reflects ____

A

how many cells were in sample

249
Q

plate dilution series to obtain ____

A

30 to 300 colonies

250
Q

samples added to agar plate using these two methods

A

spread plate method
pour plate method

251
Q

plate counts determine ____

A

colony-forming units (CFU’s)

252
Q

colony-forming units (CFU’s)

A

cells often attach to one another and form a single colony

253
Q

known volume passed through sterile filter

A

membrane filtration

254
Q

membrane filtration uses filtration to ___

A

capture and concentrate microbes

255
Q

membrane filtration filter is incubated on ____

A

appropriate agar medium

256
Q

measure cell mass instead of number of cells

A

measuring biomass

257
Q

turbidity of microbial suspension is proportional to ____

A

concentration of cells

258
Q

biomass of cells is measured with ____

A

spectrophotometer

259
Q

more cells present in sample of spectrophotometer means ____

A

less light measured

260
Q

spectrophotometer is effective only with _____

A

relatively high concentrations of cells

261
Q

standard tests correlate measured optical density to actual cell concentration

A

spectrophotometer

262
Q

total weight can be measured when measuring biomass, but

A

it can be tedious and time-consuming and is typically only used for filamentous organisms that do not readily separate into individual cells for valid plate counts

263
Q

cells in liquid culture are _____

A

centrifuged

264
Q

pellet is ____

A

weighed

265
Q

dry weight can be determined by ____

A

heating pellet in oven

266
Q

what can be used to detect cell products?

A

pH indicators
durham tubes (inverted tubes) to trap gas
CO2 production

267
Q

direct microscopic count is rapid, but at least ______ must be present to be effectively counted

A

10^7 cells/mililiter

268
Q

coulter counters and flow cytometers count ____

A

total cells in dilute solutions

269
Q

flow cytometers can be used to ____

A

count organisms to which fluorescent dues or tags have been attached

270
Q

viable cell counts require an incubation period of _____

A

approximately 24 hours

271
Q

plate counts are generally only used if the sample has _____

A

atleast 10^2 cells/mililiter

272
Q

used to count microorganisms in liquid that contain relatively few cells

A

membrane filtration

273
Q

time-consuming but technically simple method that does not require sophisticated equipment

A

plate count

274
Q

estimates the likely concentration; does not provide a precise count

A

most probable number

275
Q

biomass can be correlated to

A

cell number

276
Q

tedious and time-consuming; however, it is one of the best methods for measuring growth of filamentous microorganisms

A

total weight

277
Q

very rapid method; used routinely. a one time-correlation with plate counts is required for it to be used in determining cell number

A

turbidity

278
Q

detecting cell products are used to detect growth, but not routinely used for ____

A

quantitation

microbio (8 decks)

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