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Microbiology > microbial growth > Flashcards

microbial growth Flashcards

1
Q

What is an exception to chromosome shaped bacteria

A

borrelia burgorferi (Lyme disease) is linear

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2
Q

What is the most common mechanism for replication for bacteria

A

Binary fission

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3
Q

What are the steps of binary fission

A

cell grows and increases size and cellular components

DNA replication

formation of division septum

cell separation

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4
Q

Where does DNA replication begin during binary fission

A

on the origin of replication where the chromosome is attached to the inner cell membrane moving in opposite directions

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5
Q

where does DNA replication end during binary fission

A

the terminus

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6
Q

how many daughter cells at the end of binary fission

A

2

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7
Q

what directs cytokinesis and cell division

A

protein FtsZ

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8
Q

what does FtsZ assemble into

A

a Z ring on the cytoplasmic membrane

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9
Q

What anchors the Z ring

A

FtsZ binding proteins

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10
Q

what does the Z ring define

A

the division plane between the two daughter cells

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11
Q

what happens when addition proteins are added to the Z ring

A

it forms the divisome

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12
Q

what does the divisome do

A

activates to produce a peptidoglycan cell wall and build a septum that divides the two daughter cells

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13
Q

what is the generation time in eukaryotes

A

time between the same points of life in two successive generations

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14
Q

what is another name for generation time in prokaryotes

A

doubling time

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15
Q

what is the generation time in prokaryotes

A

the time it takes for the population to double through one round of binary fission

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16
Q

what is the generation time of E. coli.

A

20 minutes

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17
Q

what is the generation time of tuberculosis

A

15-20 hours

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18
Q

what is the generation time of M. leprae

A

14 days

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19
Q

What is a closed culture

A

a culture where no nutrients are added and no waste is removed

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20
Q

what is an example of a closed culture in nature

A

a pond

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21
Q

what is culture density

A

the number of cells per unit volume

in a closed culture it is also the number of cells in a population

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22
Q

what are the phases of the growth curve

A

lag phase
log phase
stationary phase
death or decline phase

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23
Q

what is the lag phase

A

no increase in number of living bacterial cells

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24
Q

what is the lag phase

A

exponential increase in number of living bacterial cells

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25
Q

what is the stationary phase

A

plateau in number of living bacterial cell, rate of cell death and division are roughly equal

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26
Q

what is the death phase

A

exponential decrease in number of living bacterial cells

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27
Q

what happens to cells during the Lag phase

A

they grow larger, are metabolically active, synthesize proteins to grow. repair if damaged during transfer to medium

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28
Q

what do cells do during the log phase

A

they divide by binary fission

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29
Q

what is the intrinsic growth rate

A

generation time under specific growth conditions that are genetically determined

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30
Q

what are cells in the log phase used for

A

industrial purpose due to constant growth and uniform metabolic activity

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31
Q

when are bacteria most susceptible to disinfectants and antibiotics

A

the log phase

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32
Q

what factors contribute to a slowing growth rate

A

accumulation of waste products
used up nutrients
depletion of oxygen

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33
Q

what happens to cells in the stationary phase

A

synthesis of peptidoglycan, proteins, and nucleic acids slows, sporulation in bacteria that create endospores

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34
Q

what stage are antibiotics synthesized in

A

stationary phase

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35
Q

what cells are persisters in the death phase

A

those with a slow metabolic rate.

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36
Q

what makes persisters important

A

they are associated with certain chronic infections such as TB, that do not respond to abx treatment.

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37
Q

what is an industry that keeps bacteria in a log phase

A

microbial production

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38
Q

what is a chemostat used for

A

to maintain a continuous culture where nutrients are supplied at a steady rate, a controlled amount of air is added and bacterial suspension is removed at the same rate as nutrients flow in to maintain an optimal growth environment

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39
Q

what does bacterial count indicate

A

the extent of an infection

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40
Q

what is the direct cell count method

A

counting cells in a liquid culture or colonies on a plate

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41
Q

what is the direct microscopic cell count

A

transferring a known volume of a culture to a calibrated slide and counting cells under a microscope (simplest way)

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42
Q

what is a petrol-hausser chamber

A

the calibrated slide used in direct microscopic cell count

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43
Q

what is the advantage of a petrol-hausser chamber

A

its easy to use
relatively fast
inexpensive

does not work well with dilute cultures because their mayn’t be enough cells to count

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44
Q

what are the cons of a chamber

A

does not necessarily yield an accurate count of live cells

can’t tell difference between living and dead cells

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45
Q

what does a Coulter counter do

A

detects the changes in electrical resistance in a saline solution. as a cell passes by the change in resistance is measured and the cell ocunged

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46
Q

what if a sample in Coulter counter is too dense

A

more than one cell may pass by at one time and not be counted properly skewing results,

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47
Q

does Coulter counter distinguish between live and dead cells

A

no

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48
Q

what is a plate count

A

counting colony forming units after incubation

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49
Q

what are the cons of a plate count

A

more than one cell may give rise to a colony

those that grow in clusters or chains are hard to disperse, a single colony may be many cells

some cells are viable but nonculturable

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50
Q

how many colonies on a typical plate

A

30-300

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51
Q

what happens if there are less than 30 colonies

A

it is not statistically reliable

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52
Q

what happens with colonies over 300

A

overcrowding making it difficult to count

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53
Q

how is a serial dilution made

A

1ml of culture is added to 9ml of sterile broththe process is continued until until the desired concentration is reached

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54
Q

what happens after dilution is complete

A

from each tube a sample is plated using pour plate method spread plate method and incubated until colonies appear

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55
Q

how many plates made for each dilution

A

2-3

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56
Q

What are the steps of the pour plate method

A

bacterial sample is mixed with agar

sample is our onto sterile plate

sample is swirled Tomis and allowed to solidify

plate is incubated

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57
Q

what are the steps of the spread plate method

A

sample is poured onto a solid medium

spread sample evenly over the surface
plate incubated until colonies grow

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58
Q

what is the membrane filtration technique

A

a modified plate count technique that concentrates a sample rather than diluting.

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59
Q

how does membrane filtration technique work

A

known volumes are vacuum filtered aseptically through membrane with a pore small enough to trap organisms and then transferred to a petri plate

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60
Q

how is calculation of cell density made from membrane filtration technique

A

dividing the cell count by volume of filtered liquid

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61
Q

What is most probable number

A

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

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62
Q

what is the best method for counting bacteria in water

A

membrane filtration technique

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63
Q

what is the most probable number method used for

A

water and food sampels

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64
Q

what does the MPN method evaluate

A

detectable growth by observing changes in turbidity or color due to metabolic activity

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65
Q

what is a typical application of MPN method

A

estimating coliforms in pond water

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66
Q

what are coliforms

A

gram-negative rod bacteria that ferment lactose

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67
Q

what is the presence of coliforms a sign of

A

contamination by fecal matter

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68
Q

how does the MPN method work with pond water

A

three dilutions of water is tested by inoculating five lactose broth tubes with 10ml of sample, 5 lactose broth tubes of 1ml and 5 lactose broth tubes of 0.1ml of sample with a ph indicator in the tube

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69
Q

what color on the ph indicator indicates fermentation

A

yellow

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70
Q

what do indirect cell counting methods use to estimate number

A

cell density

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71
Q

what is the most common indirect cell count

A

measuring turbidity

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72
Q

what is turbidity

A

cloudiness

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73
Q

what is a spectrophotometer

A

an instrument used to measure turbidity

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74
Q

what happens to turbidity as bacterial cell count increases

A

turbidity increases and less light can reach the detector

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75
Q

what is measuring the dry weight of a sample

A

another indirect method of evaluating culture density

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76
Q

what must happen before a dry weight of a sample is taken

A

the sample must be concentrated, washed and dried

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77
Q

what is the dry weight method good for

A

filamentous microorganisms

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78
Q

what is fragmentation

A

when many nucleotides accumulate in an enlarge round cell or along a filament and many new cels split from the parent filament and float away

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79
Q

what is a bacteria that does fragmentation

A

cyanobacteria and actinomycetes

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80
Q

describe actinomycetes

A

gram-positive, anaerobic bacteria found in soil.

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81
Q

what is budding

A

, a form of reproduction of where an organism forms a long narrow extension whose tip swells and forms a smaller cell that detaches.

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82
Q

where does budding occur

A

most commonly in yeast but in some posthecate bacteria and cyanobacteria

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83
Q

what are biofilms

A

ecosystems that form on a variety of surfaces in a liquid environment

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84
Q

what are filamentous biofilms called

A

streamers

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85
Q

where do filamentous biofilms form

A

in rapidly flowing water such as streams eddies and specially designed laboratories

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86
Q

how are streamers anchored to the substrate

A

by a head while the tail floats down stream

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87
Q

what shape do biofilms take in slow moving water

A

a mushroom-like shape

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88
Q

what is the extracellular matrix in a biofilm made of

A

extracellular polymeric substances secreted by the organisms of the biofilm

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89
Q

what percent of the biofilm is extracellular matrix

A

50-90 percent of the total dry mass

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90
Q

what is EPS

A

a hydrated gel composed of polysaccharides and other macromolecules

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91
Q

what does EPS do

A

maintains integrity and function of the biofilm

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92
Q

what are planktonic cells

A

free-floating microbial cells in an aquatic environment

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93
Q

how is a biofilm formed

A

a plankton cell attaches to as substrate

first colonizers become irreversibly attached

growth and cell division

production of EPS and formation of water channels

attachment of secondary colonizers and dispersion of microbes to new sites

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94
Q

what is an example of a metabolic collaboration in a biofilm

A

aerobic microorganisms consume oxygen, creating anaerobic regions to promote growth of anaerobes

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95
Q

what is the mechanisms where cells in a biofilm coordinate their activities

A

quorum sensing

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96
Q

what does quorum sensing do

A

enables microorganisms to detect their cell density through the releasing and binding autoinducers

97
Q

what do gram negative bacteria communicate using

A

N-acylated homoserine lactones

98
Q

what do gram positive bacteria use to communicate

A

small peptides

99
Q

when did oxygen begin rising on earth

A

when cyanobacteria started producing it and irons capacity for taking it up was exhausted

100
Q

What are some environments that are molecular oxygen free

A

deep ocean
earths crust
marshes
bogs
sewers
in parts of animal bodies

101
Q

what does a thioglycolate tube culture test for

A

different requirement of molecular oxygen

102
Q

what does autoclaving due to thioglycolate

A

flushes out most of the oxygen

103
Q

how does a thioglycolate tube culture work

A

the tube is autoclaved, inoculated and cultured at the appropriate temperature.

as oxygen diffuses bacterial density increases where the oxygen concentrations is best suited for growth

104
Q

in a thioglycolate tube culture what type of bacteria grow best at the top of the tube

A

obligate strict aerobes

105
Q

what type of bacteria grow at the bottom of a thioglycolate tube culture

A

obligate anaerobes that will likely be killed by oxygen

106
Q

what grows at the top of the tube and through out the tube

A

facultative anaerobes

107
Q

what is a facultative anaerobe

A

an organism that thrives I oxygen but also grows in its absence relying on fermentation or anaerobic respiration.

108
Q

what kind of organism grow uniformly throughout the tube

A

aerotolerant anaerobes, the are indifferent to oxygen and have a fermentative metabolism

109
Q

where do microaerophiles gather in the tube

A

just below the surface

110
Q

what are the oxygen requirements for microaerophiles

A

1-10 percent

111
Q

examples of obligate aerobes

A

mycobacterium tuberculosis
micrococcus luteus
neisseria meningitidis
n. gonorrhoeae

112
Q

what type of bacteria make up a large portion of the gut

A

obligate anaerobes mainly bacteroidetes

113
Q

what are transient anaerobic conditions

A

when tissues are not supplied with blood circulation and die breeding obligate anaerobes

114
Q

obligate anaerobes that cause infections in humans

A

C. diff
c. tetani
c. perfringens (gangrene)

115
Q

what is the most common way to grow obligate anaerobic bacteria

A

in an anaerobic jar that has chemical packs that remove oxygen and release carbon dioxide

116
Q

what is an anaerobic chamber

A

an enclosed box where all oxygen is removed

117
Q

name two examples of facultative anaerobes

A

staphylococci
enterobacteriaceae

118
Q

what do the presence of facultative anaerobes lead to

A

an environment for obligate anaerobes thrive

119
Q

what are some examples of aerotolerant anaerobes

A

lactobacilli
streptococci

120
Q

what is an example of a microaerophil

A

campylobacter jejuni

121
Q

what is minimum permissive oxygen concentration

A

the lowest concentration of oxygen that allows growth

122
Q

what is maximum permissive oxygen concentration

A

the highest tolerated concentration of oxygen

123
Q

what does. aerobic respiration generate

A

reactive oxygen species, byproducts that must be detoxified

124
Q

what enzymes break down ROS

A

superoxide dismutase
peroxidase
catalase

125
Q

what does peroxidase oxidize

A

hydrogen peroxide or other peroxides into water

126
Q

what does superoxide dismutase break down

A

superoxide anions generated by aerobic metabolism

127
Q

what does catalase breakdown

A

hydrogen peroxide to water and oxygen

128
Q

what detoxification enzymes do obligate anaerobes have

A

none

129
Q

what detoxification enzymes do aerotolerant anaerobes have

A

superoxide dismutase

130
Q

what are capnophiles

A

bacteria that grow best with high CO2 and low oxygen

131
Q

how do you grow capnophiles

A

a candle jar

132
Q

what is a candle jar

A

a jar with a tight lid that can accommodate the cultures and a candle. the candle burns out most oxygen and releases CO2

133
Q

what gives yogurt, pickles, and lime seasoned dishes the tangy taste

A

acid content

134
Q

what happens to macromolecules at a high ph

A

hydrogen bonds holding DNA break
lipids are hydrolyzed
concentration gradient collapses and impairs energy production
hydrogen bonding in amino acid functional groups is broken down

135
Q

what is optimum growth PH

A

the most favorable PH for growth of an organism

136
Q

what is minimum growth ph

A

the lowest ph an organism can candle.

137
Q

what is a maximum growth PH

A

The highest PH an organism can grow in

138
Q

what is the optimal growth ph of salmonella

A

7.0-7.5

139
Q

what is a neutrophile

A

a bacteria that grows at a pH within one two ph units of neutral

140
Q

examples of neutrophiles

A

e. coli (minus some strains)
staphylococci
salmonella

141
Q

bacteria that dont do well in stomach acid

A

some e. coli
s. typhi and other intestinal pathogens

142
Q

what ph do fungi thrive at

A

5-6

143
Q

what are acidophiles

A

microorganisms that grow optimally at a ph of less than 5.55

144
Q

examples of acidophiles

A

sulfolobus
ferroplasma
lactobacillus

145
Q

what ph do sulfolobus survive at

A

2.5-3.5

146
Q

what ph do ferroplasma live in

A

0-2.9

147
Q

what ph does lactobacillus live at

A

3.5-6.8

148
Q

what adaptations do organisms make to live at a low pH

A

proteins have increased negative surface charge to stabilize them

149
Q

what are alkaliphiles

A

microorganisms that grow best at a ph of 8-10.5

150
Q

examples of alkaliphiles

A

vibrio cholera
matron-bacterium
bacillus firmus

151
Q

what ph does cholera grow best at

A

8-10.5

grows better at 8 but can survive up to 11 and inactivated by stomach acid

152
Q

what pH does natronobacterium grow best at

A

10.5

153
Q

what adaptations do extreme alkaliphiles have

A

modifications lipid and protein structure and compensatory mechanisms to maintain proton motive

higher isoelectric point due increase in amino acids

154
Q

what is a mesophile

A

an organisms that likes moderate temperatures 20-45C

155
Q

what are examples of mesophile

A

human microbiota Ecoli, salmonella, lactobacillus

156
Q

what are psychotrophs

A

prefer cooler environments 4-25C

157
Q

what are psychotrophs responsible for

A

food spoilage of refrigerated food

158
Q

what is a psychrophile

A

cold loving organism 0C-15C

159
Q

what are thermophiles

A

organisms that grow from 50C to 80C

160
Q

examples of thermophiles

A

thermos aquaticus
geobacillus

161
Q

what’s a hyperthermophile

A

organisms that grow in 80-110C

162
Q

examples of hyperthermophiles

A

pyrobolus
pyrodictium

163
Q

effects of low temperature on macromolecules

A

membranes lose fluidity and damaged by ice crystal formation

chemical reactions slow

proteins too rigid to catalyze reactions and may denature

164
Q

how does heat affect macromolecules

A

denatures proteins
increases fluidity

165
Q

how have proteins in psychrophiles adapted

A

increase flexibility
lower number secondary stabilizing bonds
may have antifreeze proteins
unsaturated lipid membranes to increase fluidity

166
Q

adaptations in thermophiles and hyperthermophiles

A

increased ratio saturated to polyunsaturated lipids to limit fluidity
DNA has higher guanine-cytosine bases
replacement of key amino acids to stabilize folding

167
Q

what are halophiles

A

salt loving organisms that require high salt concentrations

168
Q

what are practical applications of thermoenzymes

A

degradation enzymes are added as ingredients in hot-water detergent increasing effectiveness

169
Q

what is the salt concentration of marine environments

A

3.5%

170
Q

examples of halophiles

A

red alga dunaliella salina
halobacterium

171
Q

what is the salt concentration of the great salt lake

A

3.5-8X saltier than the ocean

172
Q

what is the salt concentration of the dead sea

A

10x the ocean

173
Q

how does dunaliella counter osmotic pressure

A

which a high cytoplasmic concentration of glycerol and by pumping out salt ions

174
Q

how does halobacterium counter osmotic pressure

A

by accumulating large concentrations K and other ions in the cytoplasm

175
Q

what are halo tolerant organsism

A

tolerate salt but dont need it for growth

176
Q

example of halo tolerant organisms

A

halomonas
staphylococci
micrococci
corynebacteria
s. aureus
bacillus cereus
v cholerae

177
Q

what bacteria cause food born illness because of their ability to reproduce in food

A

s. aureus
bacillus cereus
cholerae

178
Q

what is moisture measured as

A

water activity

179
Q

what is water activity

A

the ratio of the vapor pressure of the medium of interest to the vapor pressure of distilled water

180
Q

bacteria vs fungi water requirements

A

water requires more fungi requires less

181
Q

what are ways of decreasing water content to prevent spoilage

A

drying like jerky, freeze drying, making brine and jams

182
Q

what are barophiles

A

organisms that require high atmospheric pressure

183
Q

where is large atmospheric pressure found

A

bottom of the ocean

184
Q

what is an example of an all-purpose media

A

tryptic spy broth

185
Q

what does enriched media contain

A

growth factors, vitamins, and other essential nutrients to promote growth of fastidious organisms

186
Q

what is a fastidious organisms

A

organisms that cannot make certain nutrients and need them added to the medium

187
Q

what is a chemically defined medium

A

when the complete chemical composition a medium is known

188
Q

what is an example of a chemically defined medium

A

EZ medium

189
Q

what is complex media

A

contains extracts and digests of yeasts meat or plants and the precise composition is not known

190
Q

examples of complex media

A

nutrient broth
tryptic soy broth
bran heart infusion

191
Q

what does non-selective media do

A

supports the growth of all microorganisms without any specific inhibition

192
Q

what is non-selective media used for

A

to cultivate organisms for other uses and in specific procedures

193
Q

what is an example of a non-selective media

A

mueller-hinton agar

194
Q

what is mueller Hinton agar used for

A

to test antibiotics like in the Kirby Bauer disc diffusion test

195
Q

what does mueller Hinton agar contain

A

beef extract, agar, starch

196
Q

what does starch do for mueller-hinton agar

A

supports growth, absorbs toxins and ensures abx will continue to function

197
Q

what are selective media

A

media that inhibits growth of unwanted microorganisms and support growth of the organism of interest

198
Q

how do selective media work

A

by supplying nutrients and reducing competition

199
Q

What is an example of a selective media

A

macconkey agar

200
Q

what does macconkey agar contain

A

bile salts and crystal violet that interfere with the growth of gram-positive bacteria in favor of gram negative bacteria, particularly Enterobacteriaceae

201
Q

what do enrichment cultures do

A

foster preferential growth of a desired microorganism that represents a fraction of the organisms present in an innocculum

ex bacteria that eat crude oil

202
Q

what does differential media do

A

make it easy to distinguish colonies of different bacteria by a change in color of the colonies or color of the medium

203
Q

what makes color changes in differential media

A

the result of end products created by interaction of bacterial enzymes with differential substrates or lysis of red blood cells

204
Q

what can be observed on macconkey agar

A

differential fermentation of lactose

205
Q

what color does lactose fermenters turn macconkey agar

A

hot pink due to the acid interacting with indicator neutral red

206
Q

Which of the following methods would be used to measure the concentration of bacterial contamination in processed peanut butter?

A

total plate count

207
Q

In which phase would you expect to observe the most endospores in a Bacillus cell culture?

A

death phase

208
Q

During which phase would penicillin, an antibiotic that inhibits cell-wall synthesis, be most effective?

A

log phase

209
Q

Which of the following is the best definition of generation time in a bacterium?

A

the length of time it takes for a population of cells to double

210
Q

If a culture starts with 50 cells, how many cells will be present after five generations with no cell death?

A

1600

211
Q

Filamentous cyanobacteria often divide by which of the following?

A

fragmentation

212
Q

Which is a reason for antimicrobial resistance being higher in a biofilm than in free-floating bacterial cells?

A

Cells are metabolically inactive at the base of a biofilm.

213
Q

Quorum sensing is used by bacterial cells to determine which of the following?

A

density of the population

214
Q

Which of the following statements about autoinducers is incorrect?

A

They bind directly to DNA to activate transcription.

215
Q

An inoculated thioglycolate medium culture tube shows dense growth at the surface and turbidity throughout the rest of the tube. What is your conclusion?

A

The organisms are facultative anaerobes.

216
Q

Pseudomonas aeruginosa is a common pathogen that infects the airways of patients with cystic fibrosis. It does not grow in the absence of oxygen. The bacterium is probably which of the following?

A

an obligate aerobe

217
Q

Why do the instructions for the growth of Neisseria gonorrhoeae recommend a CO2-enriched atmosphere?

A

It is a capnophile.

218
Q

Bacteria that grow in mine drainage at pH 1–2 are probably which of the following?

A

acidophiles

219
Q

Bacteria isolated from Lake Natron, where the water pH is close to 10, are which of the following?

A

alkaliphiles

220
Q

In which environment are you most likely to encounter an acidophile?

A

a hot vent at pH 1.5

221
Q

A soup container was forgotten in the refrigerator and shows contamination. The contaminants are probably which of the following?

A

psychrotrophs

222
Q

Bacteria isolated from a hot tub at 39 °C are probably which of the following?

A

mesophile

223
Q

In which environment are you most likely to encounter a hyperthermophile?

A

hydrothermal bent at the bottom the ocean

224
Q

Which of the following environments would harbor psychrophiles?

A

mountain lake with a water temperature of 12 °C

225
Q

Which of the following is the reason jams and dried meats often do not require refrigeration to prevent spoilage?

A

low water activity

226
Q

Bacteria living in salt marshes are most likely which of the following?

A

Halotolerant

227
Q

Haemophilus influenzae must be grown on chocolate agar, which is blood agar treated with heat to release growth factors in the medium. H. influenzae is described as ________.

A

fastidious

228
Q

Direct count of total cells can be performed using a ________ or a ________.

A

hemocytometer, Petroff-Hausser counting chamber

229
Q

The ________ method allows direct count of total cells growing on solid medium.

A

plate count

230
Q

A statistical estimate of the number of live cells in a liquid is usually done by ________.

A

most probable number

231
Q

For this indirect method of estimating the growth of a culture, you measure ________ using a spectrophotometer.

A

turbidity

232
Q

Active growth of a culture may be estimated indirectly by measuring the following products of cell metabolism: ________ or ________.

A

ATP, acid from fermentation

233
Q

A bacterium that thrives in a soda lake where the average pH is 10.5 can be classified as a(n) ________.

A

alkalophile

234
Q

Lactobacillus acidophilus grows best at pH 4.5. It is considered a(n) ________.

A

acidophile

235
Q

A bacterium that thrives in the Great Salt Lake but not in fresh water is probably a ________.

A

halophile

236
Q

Bacteria isolated from the bottom of the ocean need high atmospheric pressures to survive. They are ________.

A

barophiles

237
Q

Staphylococcus aureus can be grown on multipurpose growth medium or on mannitol salt agar that contains 7.5% NaCl. The bacterium is ________.

A

halotolerant

238
Q

Blood agar contains many unspecified nutrients, supports the growth of a large number of bacteria, and allows differentiation of bacteria according to hemolysis (breakdown of blood). The medium is ________ and ________.

A

complex, differential

239
Q
A

Microbiology (13 decks)

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