lecture 3 Flashcards
(278 cards)
1
Q
prokaryotic cells divide by
A
binary fission
2
Q
population doubles each division
A
exponential growth
3
Q
the time it takes for the population to double
A
generation time
4
Q
generation time varies on
A
the species and environmental conditions
5
Q
what is microbial growth defined as
A
an increase in the number of cells in a population
6
Q
what is the equation for prokaryotic growth calculation
A
N1=N0x2^n
7
Q
what does N1 mean in the microbial growth calculation
A
number of cells in population at time t
8
Q
what does N0 mean in the microbial growth calculation
A
initial number of cells
9
Q
what does n mean in the microbial growth calculation
A
number of generations at that point
10
Q
rapid generation time with optimal conditions can yield _____
A
huge populations quickly
11
Q
in nature, microbial growth usually live in
A
polymer-encased communities termed biofilms
12
Q
what do biofilms cause?
A
slipperiness of rocks in stream bed, slimy gunk in sink drains, dental plaque
13
Q
in biofilm formation, free cells _____
A
adhere to surface and multiply
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
15
Q
what gives a slimy appearance in biofilms
A
extra polymeric substances (EPS)
16
Q
where do nutrients and wastes pass through in biofilms?
A
characteristic channels
17
Q
in biofilms, cells communicate with one another via ______
A
chemical signals
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)
19
Q
biofilms can also be helpful, in cases such as _____
A
bioremediation, wastewater treatment
20
Q
microbes within biofilms are often resistant to _______
A
immune system and antibiotics
21
Q
microorganisms regularly grow in close association with ______
A
many different species
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)
23
Q
the interactions between microorganisms and different species can often be ______
A
competitive
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
25
to inhibit competitors, some microorganisms _____
synthesize toxic compounds
26
population of cells derived from a single cell; allows study of a single species
pure culture
27
in pure cultures, organisms may _____
behave differently than in nature
28
what percent of microorganisms can be cultured?
1%
29
pure culture obtained (and maintained) using _____
aseptic technique
30
aseptic techniques minimize ____
accidental introduction of other organisms
31
cells grow in or on culture medium contain
nutrients dissolved in water
32
cells grow in or on culture medium can be
liquid broth or solid gel
33
what do you need to obtain a pure culture?
culture medium, container, aseptic conditions, method to separate individual cells
34
what happens in correct conditions when a pure culture is obtained?
a single cell will multiply to form a visible colony (approximately 1 million cells easily visible)
35
what is used to solidify a medium in a pure culture
agar
36
why is agar a good solidifier for the medium
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
37
a pure culture is grow in a
petri dish
38
petri dish with agar nutrient medium
agar plate
39
two-part covered container of glass or plastic
allows air to enter, but excludes contaminants
petri dish characteristics
40
simplest, most commonly used method for isolating in obtaining a pure culture
streak-plate method
41
what does the streak-plate method do?
reduces number of cells with each series of streaks
42
what do separated cells do in the streak-plate method?
form distinct, isolated colonies
43
a pure culture can be maintained as a ______
stock culture
44
what is a stock culture often stored as?
agar slant
45
cells can be frozen at ______ for long-term storage
-70 degrees celsius
46
what are cells mixed with for long term storage?
glycerol to prevent ice crystal formation
47
stock cultures can be ____ for storage
freeze-dried
48
culture in which nutrients are not added, nor are wastes removed
closed system
49
closed systems are also called
batch cultures
50
closed systems include
microorganisms grown on agar plates or in tubes or flasks of broth
51
what is seen in closed broth culture?
characteristic growth curve
52
number of cells does not increase
cells begin synthesizing enzymes required for growth
delay depends on conditions
lag phase
53
at which stage do cells divide at a constant rate?
exponential (log) phase
54
what happens when cells are dividing at a constant rate?
generation time measured,
most sensitive to antibiotics
55
what is formed during the exponential (log) phase?
primary metabolites, secondary metabolites
56
example of primary metabolites
amino acids
57
what are secondary metabolites produced as?
secondary metabolites such as antibodies are produced as nutrients and depleted, leading to waste accumulation
58
phases of the growth curve
lag phase
exponential (log) phase
stationary phase
death phase
phase of prolonged decline
59
nutrient levels too low to sustain growth
total number remain constant
stationary phase
60
in the stationary phase, what occurs?
some cells die, releasing nutrients; others grow
continue to produce secondary metabolites
61
total number of viable cells decreases
death phase
62
what happens in the death phase?
cells die at constant rate
exponential, but usually much slower than cell growth
63
phase of prolonged decline
some fraction may survive, and they are adapted to tolerate worsened conditions
64
growth of bacteria on solid medium and liquid broth is similar, but ______
there are important differences
65
____ of single cell in a colony determines its environment
position
66
edge of colony
little competition for O2, nutrients
67
center of colony
depleted O2, nutrients
accumulation of potentially toxic wastes
68
cells at edges of colony may show ______ while those in the center are in the ______
exponential growth, death phase
69
culture to which nutrients are continually added and waste products removed
open system
70
provides an open system that can maintain continuous growth
chemostat
71
in a chemostat, ______ and ______ can be controlled to achieve constant growth rate and cell density
nutrient content, speed of addition
72
a chemostat produces ______
relatively uniform population to study response to different conditions
73
a chemostat can maintain cells in _____
log phase of growth to harvest commercially valuable products
74
as a group, microorganisms inhabit _____
nearly all environments
75
extremophiles live in
harsh environments
76
most extremophiles are
archaea
77
major factors that affect microbial growth
temperature
atmosphere
pH
water availability
78
environmental factors that influence microbial growth
temperature
oxygen availability
pH
water availability
79
types of temperature as an environmental factor
psychrophile
psychrotroph
mesophile
thermophile
hyperthermophile
80
types of oxygen availability as an environmental factor
obligate aerobe
facultative anaerobe
obligate anaerobe
microaerophile
aerotolerant anaerobe
81
types of pH as an environmental factor
neutrophile
acidophile
alkalophile
82
types of water availability as an environmental factor
halotolerant
halophile
83
thermostability appears to be due to protein structure
temperature
84
optimum temperature between -5 degrees celsius and 15 degrees celsius
psychrophile
85
optimum temperature between 15 degrees celsius and 30 degrees celsius, but grows well at refrigeration temperatures
psychrotroph
86
optimum temperature between 25 degrees celsius and 45 degrees celsius
mesophile
87
optimum temperature between 45 degrees celsius and 70 degrees celsius
thermophile
88
optimum temperature of 70 degrees celsius or greater
hyperthermophile
89
oxygen requirement/tolerance reflects the organisms's energy harvesting mechanisms and its ability to inactivate reactive oxygen species
oxygen availability
90
requires O2
obligate aerobe
91
grows best if O2 is present, but can also grow without it
facultative anaerobe
92
cannot grow in the presence of O2
obligate anaerobe
93
requires small amounts of O2, but higher concentrations are inhibitory
microaerophile
94
indifferent to O2
aerotolerant anaerobe (obligate fermenter)
95
prokaryotes that live in pH extremes maintain a near-neutral internal pH by ________
pumping protons out of or into the cell
96
multiplies in the range of pH 5 to 8
neutrophile
97
grows optimally at a pH below 5.5
acidophile
98
grows optimally at a pH above 8.5
alkalophile
99
prokaryotes that can grow in high-solute solutions maintain the availability of water in the cell by ______
increasing their internal solute concentration
100
can grow in relatively high-salt solutions, up to approximately 10% NaCl
halotolerant
101
requires high levels of sodium chloride
halophile
102
where are psychrophiles found?
in arctic and antarctic regions
103
what are psychotrophs important in?
spoilage of refrigerated foods
104
mesophile pathogens live in _____
35 degrees to 40 degrees celsius
105
thermophiles are common in _____
hot springs and compost heaps
106
hyperthermophiles are usually _____
archaea
107
hyperthermophiles are found in _____
hydrothermal vents
108
solidified agar slows _____
gas diffusion
109
top of shake tube is _____
aerobic
110
bottom of shake tube is _____
anaerobic
111
steps of measuring in shake tube
1) boil nutrient agar to drive off O2
2) cool to just above solidifying temperature
3) add microorganisms
4) gently swirl
112
requires O2 for respiration
obligate aerobe
113
uses O2 for respiration, if available
facultative anaerobe
114
does not use O2 for respiration
obligate anaerobe
115
requires O2 for respiration
microaerophile
116
does not use O2 for respiration (2)
aerotolerant anaerobe
117
produces superoxide dismutase and catalase to protect against reactive oxygen species
obligate aerobe
118
produces superoxide dismutase and catalase to protect against reactive oxygen species (2)
facultative anaerobe
119
does not produce superoxide dismutase or catalase to protect against reactive oxygen species
obligate anaerobe
120
produces some superoxide dismutase and catalase to protect against reactive oxygen species
microaerophile
121
produces superoxide dismutase but not catalase to protect against reactive oxygen species
aerotolerant anaerobe
122
bacterial growth at the top of test tube
obligate aerobe
123
grows throughout test tube, but most growth is at the top of tube
facultative anaerobe
124
grows at the bottom of the test tube
obligate anaerobe
125
grows near the top of the test tube, but not all the way at the top
microaerophile
126
grows equally throughout the test tube
aerotolerant anaerobe
127
harmful by-products of using O2 in aerobic respiration
reactive oxygen species (ROS)
128
reactive oxygen species include
superoxide and hydrogen peroxide
129
reactive oxygen species are damaging to ____
cellular components
130
cells must have ____
protective mechanisms
131
obligate anaerobes typically do not have _____
protective mechanisms
132
almost all organisms growing in presence of oxygen produce ______
enzyme superoxide dismutase
133
superoxide dismutase inactivates ______
superoxide
134
how does superoxide dismutase inactivate superoxide?
by converting it to O2 and H2O2
135
almost all organisms also produce _____
catalase
136
catalase converts _____
H2O2 to O2 and H2O
137
what does not produce catalase?
aerotolerant anaerobes (makes for useful test)
138
bacteria survive a range of pH, but they have _____
an optimum
139
most bacteria maintain constant internal pH, which is typically _____
near neutral
140
bacteria pump out protons if in ____
acidic environment
141
bacteria bring in protons if in ______
alkaline environment
142
what is the optimum of a neutrophile?
near pH 7
143
most microbes are _____
neutrophiles
144
food can be preserved by ______
increasing acidity
145
where does H. pylori grow?
stomach
146
what does H. pylori produce?
urease
147
H. plyori produces urease to _____
split urea into CO2 and ammonia to decrease acidity of surroundings
148
what has optimum pH of less than 1
picrophilus oshimae
149
all microorganisms require _____ for growth
water
150
what makes water unavailable to cell?
dissolved salts, sugars
151
if solute concentration is higher outside of cell, water ______
diffuses out
152
what is used to preserve food?
salt, sugar
153
some microbes withstand or even require
high salt
154
example of halotolerant
staphylococcus on dry salty skin
155
marine bacteria is a _____
halophile, requires approximately 3 % salt
156
extreme halophiles require
> 9 % (dead sea, utah's salt flats)
157
_____ required to synthesize cell components
nutrients
158
major elements
carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, magnesium, calcium, and iron
159
trace elements
cobalt, zinc, copper, molybdenum, manganese
160
prokaryotes can use diverse sources to _____
acquire various elements
161
component of amino acids, lipids, nucleic acids, and sugars
carbon, oxygen, and hydrogen
162
component of amino acids and nucleic acids
nitrogen
163
component of some amino acids
sulfur
164
component of nucleic acids, membrane lipids, and ATP
phosphorus
165
required for the functioning of certain enzymes; additional functions as well
potassium, magnesium, and calcium
166
part of certain enzymes
iron
167
carbon source distinguishes
different groups
168
uses organic carbon
heterotrophs
169
use inorganic carbon as CO2
autotrophs
170
converts inorganic carbon to organic form
carbon fixation
171
_____ required for amino acids, nucleic acids
nitrogen
172
converting N2 gas to ammonia and then incorporating it into organic compounds
nitrogen fixation
173
most organisms use ______
ammonia or aminonitrogen (some convert nitrate to ammonia)
174
______ are often limiting nutrients
phosphorus and iron
175
limiting nutrients available at
lowest concentrations relative to need
176
limiting nutrients dictate
maximum level of microbial growth
177
organic molecules that an organism cannot synthesize; must be present in the environment
growth factors
178
growth factor requirements reflect
biosynthetic capabilities
179
Most ______ synthesize all cellular components from glucose; no growth factors needed
E. Coli
180
Neisseria species are _____
fastidious (they require numerous growth factors, including vitamins and amino acids)
181
fastidious species can be used to ____
measure the quantity of vitamins in food products
182
energy sources
sunlight, chemical compounds
183
obtain energy from sunlight
phototrophs
184
example of phototrophs
plants, algae, photosynthetic bacteria
185
extract energy from chemicals
chemotrophs
186
what extract energy from organic molecules?
mammalian cells, fungi, many types of prokaryotes
187
common sources of organic molecules
sugars, amino acids, fatty acids
188
some prokaryotes extract energy from _____
inorganic chemicals
189
examples of inorganic chemicals
hydrogen sulfide, hydrogen gas
190
energy from sunlight; carbon from CO2
photoautotrophs
191
energy from sunlight; carbon from organic compounds
photoheterotrophs
192
energy from inorganic compounds; carbon from CO2
chemolithoautotrophs
193
what are chemolithoautotrophs also termed as
chemoautotrophs, chemolithotrophs
194
energy and carbon from organic compounds
chemoorganoheterotrophs
195
chemoorganoheterotrophs are also termed as
chemoheterotrophs, chemoorganotrophs
196
contain a variety of ingredients
complex media
197
the exact composition of complex media is _____
highly variable
198
composed of exact amounts of pure chemicals
chemically defined media
199
chemically defined media exhibit typically _____
slower growth as cells must synthesize components
200
complex medium used routinely in clinical labs. differential because colonies of hemolytic organisms are surrounded by a zone of red blood cell clearing.
blood agar
201
complex medium used to culture fastidious bacteria, particularly those found in clinical specimens.
chocolate agar
202
blood agar is
not selective
203
chocolate agar is
not selective or differential
204
chemically defined medium. used in laboratory experiments to study nutritional requirements of bacteria
glucosesalts agar
205
glucosesalts agar are
not selective or differential
206
complex medium used to isolate gram-negative rods that typically reside in the intestine
MacConkey agar
207
MacConkey agar is selective because
bile salts and dyes inhibit Gram-positive organisms and Gram-negative cocci
208
MacConkey agar is differential because
the pH indicator turns pink-red when the sugar in the medium, lactose, is fermented
209
nutrient agar is
not selective or differential
210
complex medium used for routine labratory work. supports the growth of a variety of nonfastidious bacteria
nutrient agar
211
ThayerMartin agar is not
differential
212
ThayerMartin agar is selective because
it contains antibiotics that inhibit most organisms except Neisseria species
213
complex medium used to isolate neisseria species, which are fastidious
ThayerMartin agar
214
E. coli can grow in ____
complex media or chemically defined media
215
nutrient broth is also known as
complex medium
216
glucose-salts broth is also known as
chemically defined medium
217
peptone is the complex medium, what is the chemically defined medium?
glucose
218
beef extract is the complex medium, what is the chemically defined medium?
dipotassium phosphate
219
water is the complex medium, what is the chemically defined medium?
monopotassium phosphate
magnesium sulfate
ammonium sulfate
calcium chloride
iron sulfate
water
220
inhibit growth of certain species in a mixed sample, while allowing growth of species of interest
selective media
221
MacConkey agar is selective for
Gram-negative rods
222
MacConkey agar is differential for
lactose fermentation
223
MacConkey agar contains
crystal violet that inhibits Gram-positive bacteria and bile salts that inhibit most non-intestinal bacteria
224
contain substance that microbes change in identifiable way
differential media
225
beta hemolysis of blood agar produces
clear zone
226
alpha hemolysis of blood agar produces
zone of greenish partial clearing
227
selective or differential media can be used to
detect or isolate a species from a mixed population
228
most obligate aerobes and facultative anaerobes can be incubated in _____
air (approximately 20% O2)
229
broth cultures are shaken to ____
provide maximum aeration
230
many medically important bacteria (for example, Neisseria, Hemophilus) grow best with ____
increased CO2
231
one method to increase CO2 is to
incubate in candle jar
232
capnophiles
meaning requires increased CO2
233
require lower O2 concentrations than achieved by candle jar
microaerophilic
234
microaerophiles can incubate in
gas-tight container with chemical packet
(chemical reaction reduces O2 to 5 to 15%)
235
obligate anaerobes sensitive to O2 are
anaerobic
236
anaerobe containers are useful if
microbe can tolerate brief O2 exposures (can also use semisolid culture medium containing reducing agent such as sodium thioglycolate)
237
reducing agents in anaerobe containers can reduce ____
O2 to water
238
anaerobic chamber provides
more stringent approach
239
used to isolate organism present as only a small fraction of mixed population
enrichment culture
240
enrichment cultures provide
conditions promoting growth of particular species
241
in an enrichment culture, the _______ increases
relative concentration of target organism
242
direct cell counts find ______
total numbers of cells (living plus dead)
243
cell-counting instruments
coulter counter
flow cytometer
244
direct cell counts can be found with ____
direct microscopic count
245
viable cell counts find ____
cells capable of multiplying, the number of microorganisms capable of growing in a given set of conditions
246
viable cell counts can use _____
selective, differential media for particular species (can determine the number of specific microbial species)
247
single cell gives rise to colony
plate counts
248
number of colonies in a plate count reflects ____
how many cells were in sample
249
plate dilution series to obtain ____
30 to 300 colonies
250
samples added to agar plate using these two methods
spread plate method
pour plate method
251
plate counts determine ____
colony-forming units (CFU's)
252
colony-forming units (CFU's)
cells often attach to one another and form a single colony
253
known volume passed through sterile filter
membrane filtration
254
membrane filtration uses filtration to ___
capture and concentrate microbes
255
membrane filtration filter is incubated on ____
appropriate agar medium
256
measure cell mass instead of number of cells
measuring biomass
257
turbidity of microbial suspension is proportional to ____
concentration of cells
258
biomass of cells is measured with ____
spectrophotometer
259
more cells present in sample of spectrophotometer means ____
less light measured
260
spectrophotometer is effective only with _____
relatively high concentrations of cells
261
standard tests correlate measured optical density to actual cell concentration
spectrophotometer
262
total weight can be measured when measuring biomass, but
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
cells in liquid culture are _____
centrifuged
264
pellet is ____
weighed
265
dry weight can be determined by ____
heating pellet in oven
266
what can be used to detect cell products?
pH indicators
durham tubes (inverted tubes) to trap gas
CO2 production
267
direct microscopic count is rapid, but at least ______ must be present to be effectively counted
10^7 cells/mililiter
268
coulter counters and flow cytometers count ____
total cells in dilute solutions
269
flow cytometers can be used to ____
count organisms to which fluorescent dues or tags have been attached
270
viable cell counts require an incubation period of _____
approximately 24 hours
271
plate counts are generally only used if the sample has _____
atleast 10^2 cells/mililiter
272
used to count microorganisms in liquid that contain relatively few cells
membrane filtration
273
time-consuming but technically simple method that does not require sophisticated equipment
plate count
274
estimates the likely concentration; does not provide a precise count
most probable number
275
biomass can be correlated to
cell number
276
tedious and time-consuming; however, it is one of the best methods for measuring growth of filamentous microorganisms
total weight
277
very rapid method; used routinely. a one time-correlation with plate counts is required for it to be used in determining cell number
turbidity
278
detecting cell products are used to detect growth, but not routinely used for ____
quantitation
