Lecture 3 Microbial Growth 2.0 Flashcards
(154 cards)
1
Q
Prokaryotic cells divide by
A
Binary fission
2
Q
What type of growth do prokaryotic cells divide by?
A
Exponential growth: population doubles each division
3
Q
What is an example of exponential growth starting with 2?
A
2, 4, 8, 16, 32
4
Q
What time does it take for the population to double?
A
Generation time
5
Q
Microbial growth is defined as an _______ in the number of cells in a population
A
Increase
6
Q
What is Nt?
A
Number of cells in a population at time, t
7
Q
What is N0?
A
Initial number of cells
8
Q
What is n?
A
Number of generations at that point?
9
Q
Most bacteria attach to surfaces and live in polymer encased communities called _________
A
Biofilms
10
Q
Step 1 of biofilm
A
Free cells adhere to surface and multiple
11
Q
Step 2 of biofilm
A
Release polymers to which unrelated cells may attach and grow
12
Q
Step 3 of biofilm
A
Extra polymeric substances (EPS) give slimy appearances
13
Q
Step 4 of biofilm
A
Nutrients and wastes pass through characteristic channels
14
Q
Step 5 of biofilm
A
Cells communicate with one another via chemical channels
15
Q
Dental plaque is _______
leads to ______ and _____
A
Biofilm
Tooth decay, gum disease
16
Q
Most _________ seem to involve biofilm
A
infection
17
Q
Microbes within bioflims are often ______ to immune system and antibiotics
A
Resistant
18
Q
What is the industrial concern of biofilms?
A
Accumulation in pipes, dranes
- hundreds of times more resistant to disinfectants
19
Q
Biofilms are helpful for what?
A
Bioremediation, wastewater treatment
20
Q
Microorganisms regularly grow in close association with many different _______
A
species
21
Q
Strict anareobes can grow in mouth if others consume ______
A
O2
22
Q
Metabolic waste can serve as ______ of other
A
Nutrient
23
Q
Interactions of mixed microbial communities are
A
Competitive
24
Q
Some gram negative bacteria ______ system to inject toxic compounds directly into competing bacteria
A
Type VI secretion system
25
What is pure culture?
Population of cells derived from a single cell
allows study of a single species
26
What is an enrichment culture?
Used to isolate organism present as only a SMALL fraction of mixed population
27
In enrichment cultures, relative concentration of target organism increases or decreases?
Increases
28
What is direct cell counts
Total number
Living + dead
29
What are cell counting instruments?
Coulter counter, flow cytometer
30
How is total cell count determined? (equation)
1/volume held in square (in mL)
Then multiple that by number of cells
31
What is viable cell count?
Cells capable of multiplying
32
What media is used for viable cell counts?
selective, differential
33
What is plate counts
Single cell gives rise to coony
34
What shows how many cells were in a sample?
Number of colonies
35
Plate gets diluted to obtain how many colonies to produce a countable plate?
30 to 300
36
What to plate counts determine?
Colony forming unites (CFUs)
37
What is membrane filtration?
Known volume is passed through a sterile filter
Filter is incubated on agar medium
38
What does membrane filtration do?
It captures and concentrates microbes by filtration
39
How do you measure biomass?
Measure cell mass instead of number of cells
40
Turbidity of microbial suspension is proportional to what?
Concentration of cells
41
What measures biomass?
Spectrophotometer
42
What does a spectrophotometer show?
more cells present = less light
43
spectrophotometer measurement is effective only for what?
High concentration of cells
44
How is pure culture obtained?
Aseptic technique
45
Cells grown on pure culture contain nutrients dissolved in water, can be _______ or _______
liquir broth or solid gel
46
In a pure culture, single cell will multiply to form a _______
colony (aprox. 1 million cells)
47
What is used to solidify medium?
Agar
48
What can enter in a petri dish?
air, excludes contaminants
49
What is the simplest, most common method for isolating
Streak-plate method
50
After incubation of a streak plate, what do separate cells form
distinct, isolated colonies
51
a pure culture can be maintained as what/
stock culture
52
How is a stock culture maintained?
Stored in fridge as agar slant
cells can be frozen at -70 degrees for long term
mized with glycerol to prevent ice crystal formation
Can be freeze fried
53
What is a closed system?
Culture in which nutrients are not added, nor waste is remoced
54
What does a closed system include
Microorganisms grown on agar plates or in tubes or flasks of broth
55
What curve is seen in closed broth culture?
Growth curve
56
in a lag phase, what happens to number of cells?
Does not increase
57
what do the cells begin doing in a lag phase?
synthesizing enzymes required for growth
58
in an expontential (Log) phase, what rate do cells divide at?
constant rate
59
What is measured in the log phase?
Generation time
60
What does the log phase produce?
primary metabolites
61
What is produced as nutrients are depleted and wastes accumulate?
Secondary metabolites
62
What happens in the stationary phase
- nutrient levels are_______
- total numbers are _______
- continue to produce _______
too low to sustain growth
remain constant
secondary metabolites
63
What happens in the death phase
- total number of cells _______
- cells die at a _______ rate
- grows _______ but slow
decrease
constant
exponential
64
Phase of prolonged decline
- some fraction _______
- adapted to tolerate _______ conditions
survive
worsened
65
position of a single cell in a colony determines its _______
environment
66
What does the edge of a colony mean?
Little competition for O2 and nutrients
67
What does the center of colony mean?
Depleted O2, accumulation of potentially toxic wastes
68
Cells at edge of colony may show _______ growth
Exponential
69
cells in the center of a colony are in the _______ phase
death
70
What is an open system?
Culture to which nutrients are continually added and waste products removed
71
What is a chemostat?
Provides an open system that can maintain continuous growth
72
in a chemostat
- nutrient content and speed of addition can be controlled to achieve _______ growth rate and cell density
- produces relatively _______ population to study response to different conditions
- can maintain cells in _______ phase of growth to harvest commercially valuable products
constant
uniform
log
73
What are extremophiles
Bacteria that live in harsh environments
74
What are most of extremophiles?
Archaea
75
What are the major factors that affect microbial growth?
Temperature, atmosphere, pH, water availability
76
Degree of psychrophiles
-5 to 15
77
degree of psychotrophs
15 to 30
78
degree of mesophiles
25 to 45
79
degree of thermophiles
45 to 70
80
degree of hyperthermophiles
70>
81
Where are psychotrophiles found?
arctic and antarctic regions
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What is psychrotrophs important for?
spoilage of refrigerated foods
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Thermophiles are common where?
hot springs, compost heaps
84
Hypertherophiles are usually _______
found _______
Archaea
hydrothermal vents
85
Solidified agar _______ gas diffusion
Slows
86
In solidified agar,
- top is _______
- bottom is _______
Aerobic
Anaerobic
87
What does the position of growth indicate?
O2 requirements
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obligate aerobes O2 requirement
Requires O2
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Facultative aerobes O2 requirement
Use O2 but don't require it
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Obligate anaerobes O2 requirements
Cannot use O2
91
Microaerophiles O2 requirement
Require small amounts of O2 only
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Aertolerant anaerobes (obligate fermenters)
Can grow O2 but don't use it
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What are Reactive Oxygen Species
Harmful by-products of using O2 in aerobic respiration
94
What are the two reactive oxygen species?
O2 and H2O2
95
What is the affect of ROS?
Damages cellular components
96
What bacteria don't have the protective mechanisms against ROS?
obligate anaerobes
97
Almost all organisms growing in presence of oxygen produce which enzyme?
Superoxide dismutase
98
What does superoxide dismutase do?
Inactivates superoxide by converting it to O2 and H2O2
99
What does catalse do?
Converts H2O2 ---> O2 and H2O
100
What is the exception to catalase?
Aerotolerant anaerobes
101
Most bacteria have what pH?
neutral
102
What do bacteria do if they are in an acidic environment?
Pump out protons H
103
What do bacteria do if they are in an alkaline environment?
Bring in protons H
104
Most microbes are
Neutrophiles
105
What is the pH range of neutrophiles
5-8, optimum is 7
106
Food can be preserved by increasing
Acidity
107
What bacteria grows in stomach and produces urease to split urea into CO2 and ammonia?
H. pylori
108
What does H. pylori do to the acidity of the surroundings?
Decreases
109
What bacteria grow optimally at pH below 5.5
Acidophiles
110
Which bacteria has an optimum pH of less than 1
Picrophilus oshimae
111
What bacteria grow optimally at pH above 8.5
Alkaliphiles
112
All organisms require what for growth?
water
113
If solute concentration is higher outside of the cell, what happens?
Water diffuses out, osmosis
114
Halotolerant
Withstands up to 10% sald
115
What type of bacteria is staphylococcus in regards to salt tolerance?
Halotolerant
116
What is halophiles
Requires high salt levels
117
What are the major nutritional elements for prokaryotes
carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, magnesium, calcium, iron
118
What type of carbon to heterotrophs use?
Organic carbon
119
What type of carbon to autotrophs use
inorganic carbon
120
What is carbon fication
Converts inorganic carbon to organic carbon
121
What is nitrogen required for?
Amino acids, nucleic acids
122
What is nitrogen fixation?
Converts N2 gas to ammonia and incorporates into organic compounds
123
Most organisms use what nitrogen?
ammonia or aminonitrogen
124
Phospohrus and iron are _______ nutrients
Limiting
125
What are growth factors
Organic molecules that an organism cannot synthesize
126
What is fastidious
requires specific and many growth factors to survive
127
What are phototrophs
obtain energy from sunlight
128
What are chemotrophs
Extract energy from chemicals
129
Photoautotrophs
Energy from sunlight, carbon from CO2
130
Photoheterotrophs
Energy from sunlight, carbon from organic compounds
131
Chemolithoautotrophs
Energy from inorganic compounds, carbon fro CO2
132
Chemoorganoheterotrophs
Energy and carbon from organic compounds
133
What is complex media
Contains variety of ingredients, exact composition is highly variable
134
What is chemically defined media?
Composed of exact amounts of pure chemicals
135
is chemically defined media or complex media faster?
Complex media... Chemically defined is slower as cells must synthesize components
136
What can grow in complex and chemically defined media?
E. coli
137
What is selective media
Inhibits growth of certain species in a mixed sample, allows growth of species of interest
138
MacConkey agar is selective for what/
Gram negative rods
139
MacConkey agar is differential for what?
Lactose fermentation
140
What is selective media made up of?
Crystal violet that inhibits gram positive bacteria
bile salts that inhibit non-intestinal bacteria
141
What is differential media?
Contains substance that microbes change in identifiable way
142
What type of media is blood agar?
Differential
143
in blood agar, what does beta hemolysis do?
produces clear zone
144
In blood agar, what does alpha hemolysis do?
Produces zone of greenish partial clearing
145
REFER TO SLIDE 38 for pictures
Which one could be MacConkey?
THIS IS ON EXAM.... MUST REVIEW
Differential
146
Where can aerobes and facultative anaerobes be incubated?
in air, 20% O2
147
Where do medically important bacteria (aerobes) grow best in?
Increased CO2
148
Some medically important aerobes are
Capnophiles...REQUIRE increased CO2
149
What method is used to incubate capnophiles?
Candle jar
150
What does the microaerophilic require?
Lower O2 concentration achieved by candle jar
151
How do you give optimal growth for microaerophilic bacteria?
Gas tight contain with chemical packet
152
Obligate anaerobes are sensitive to
O2
153
Anearobes are put into anaerobic containers if they can tolerate
Brief O2 exposure
154
What are ways to detect cell products?
pH indicators, Durham tubes (inverted tubes to trap gas), CO2 productions
