Ch. 5 Flashcards
1
Q
Growth-
A
Increase in the number of cells
2
Q
Binary fission-
A
Cell division following enlargement of a cell to twice its minimum size
3
Q
Generation time-
A
Time required for microbial cells to double in number
4
Q
During cell division, each daughter cell receives a chromosome and sufficient copies of all other cell constituents to exist as an ___ ___.
A
Independent cell
5
Q
Most bacteria have shorter ___ ___ than eukaryotic microbes.
A
Generation times
6
Q
___ ___ is dependent on growth medium and incubation conditions.
A
Generation time
7
Q
Exponential growth-
A
Growth of a microbial population in which cell numbers double within a specific time interval
8
Q
During ___ ___, the increase in cell number is initially slow but increases at a faster rate.
A
Exponential growth
9
Q
Batch culture-
A
A closed-system microbial culture of fixed volume
10
Q
Typical growth curve for population of cells grown in a closed system is characterized by four phases:
A
- lag phase
- exponential phase
- stationary phase
- death phase
11
Q
Lag phase-
A
Interval between inoculation of a culture and beginning of growth
12
Q
Exponential phase-
A
Cells in this phase are typically in the healthiest state
13
Q
Stationary phase-
A
- growth rate of a population is zero
- either an essential nutrient is used up, or waste product of the organism accumulates in the medium
14
Q
Death phase-
A
If incubation continues after cells reach stationary phase, the cells will eventually die
15
Q
Continuous culture-
A
An open-system microbial culture of mixed volume
16
Q
Chemostat-
A
Most common type of continuous culture device
17
Q
Both growth rate and population density of culture can be controlled ___ and ___.
A
Independently and simultaneously
18
Q
Dilution rate-
A
Rate at which fresh medium is pumped in and spent medium is pumped out
19
Q
In a chemostat the growth rate is controlled by ___ ___.
A
Dilution rate
20
Q
In a chemostat the growth yield is controlled by the concentration of the ___ ___.
A
Limiting nutrient
21
Q
In a ___ ___, growth conditions are constantly changing; it is impossible to independently control both growth parameters.
A
Batch culture
22
Q
___ ___ are sensitive to the dilution rate and limiting nutrient concentration.
A
Chemostat cultures
23
Q
Chemostat cultures
At too high a dilution rate, the organism is..
A
Washed out
24
Q
Chemostat cultures
At too low a dilution rate, the cells may..
A
Die from starvation
25
Chemostat cultures
Increasing concentration of a limiting nutrient results in..
Greater biomass but same growth rate
26
Microbial cells are enumerated by ___ ___.
Microscopic observations
27
Limitations of microscopic counts:
- cannot distinguish between live and dead cells without special stain
- small cells can be overlooked
- precision is difficult to achieve
- phase-contrast microscope required if a stain is not used
- cell suspensions of low density hard to count
- motile cells need to be immobilized
- debris in sample can be mistaken for cells
28
A second method for enumerating cells in liquid samples is use of a ___ ___.
Flow cytometer
29
Flow cytometer-
A second method for enumerating cells in liquid samples
30
A flow cytometer uses:
Laser beams, fluorescent dyes, and electronics
31
Viable cell counts (plate counts):
Measurement of living, reproducing population
32
Two main ways to perform plate counts:
- spread-plate method
| - pour-plate method
33
The obtain the appropriate ___ ___, the sample to be counted should always be diluted.
Colony number
34
___ ___ can be highly unreliable when used to assess total cell numbers of natural samples.
Plate counts
35
The great plate anomaly-
Direct microscopic counts of natural samples reveal far more organisms than those recoverable on plates
36
Microscopic methods count ___ ___, whereas viable methods do not.
Dead cells
37
Different organisms may have vastly different requirements for ___.
Growth
38
Turbidity measurements-
- Indirect, rapid, and useful methods of measuring microbial growth
- quick and easy to perform
- typically do not require destruction or significant disturbance of sample
- sometimes problematic
39
Most often turbidity is measured with a ___.
Spectrophotometer
40
Most often turbidity is measured with a spectrophotometer, and measurement is referred to as ___ ___.
Optical density
41
To relate a direct cell count to a turbidity value, a ___ ___ must first be established.
Standard curve
42
___ is a major environment factor controlling microbial growth.
Temperature
43
Cardinal temperatures-
The minimum, optimum, and maximum temperatures at which an organism grows
44
Microorganisms can be classified into groups by their ___ ___ ___.
Growth temperature optima
45
Psychrophile-
Low temperature optima
Inhabit permanently cold environments
46
Mesophile-
Midrange temperature optima
47
Thermophile-
High temperature
Growth temperature optima between 45C and 80C
48
Hypertheromophile-
Very high temperature
Optima greater than 80C
49
Mesophiles are found in:
- warm-blooded animals
- terrestrial and aquatic environments
- temperate and tropical latitudes
50
Extremophiles-
Organisms that grow under very hot or very cold conditions
51
Psychrotolerent-
Organisms that can grow 0C but have optima of 20C to 40C
52
___ are more widely distributed in nature than psychrophiles.
Psychrotolerant
53
Where can you find hyperthermophiles?
Hot environments, including boiling hot springs and seafloor hydrothermal vents, than can experience temperature in excess of 100C
54
Hyperthermophiles in hot springs
- chemoorganotrophic and chemolithotrophic species are present
- high prokaryotic diversity
55
Hyperthermophiles produce enzymes widely used in ___ ___.
Industrial microbiology
56
The ___ of an environment greatly affects microbial growth.
pH
57
Some organisms have evolved to grow best at low or high pH, but most organisms grow best between pH __ and __.
6 and 8 (neutrophiles)
58
Acidophiles-
Organisms that grow best at low pH (less than 6)
59
What happens to obligate acidophiles when they are exposed to a neutral pH?
Membranes are destroyed
60
Alkaliphiles-
Organisms that grow best at high pH (greater than 9)
61
The internal pH of a cell must stay relatively close to ___ even though the external pH is highly acidic or basic.
Neutral
62
Internal pH has been found to be as low as ___ in extreme acidophiles.
4.6
63
Internal pH has been found to be as high as ___ in extreme alkaliphiles.
Alkaliphiles
64
Halophiles-
Organisms that grow best at reduced water potential; have a specific requirement for NaCl
65
What's an example of a halophile?
Allivibrio fischeri
66
___ are organisms that grow best at reduced water potential.
Halophiles
67
Extreme halophiles-
Organisms that require high levels (15-30%) or NaCl for growth
68
What is an example of an extreme halophile?
Halobacterium salinarum
69
___ ___ are organisms that require high levels of NaCl for growth.
Extreme halophiles
70
Halotolerant-
Organisms that can tolerate some reduction in water activity of environment but generally grow best in the absence of the added solute
71
What is an example of a halotolerant?
Staphylococcus aureus
72
Osmophiles-
Organisms that live in environments high in sugar as solute
73
___ are organisms that live in environments high in sugar as solute.
Osmophiles
74
Xerophiles-
Organisms able to grow in very dry environments
75
___ are organisms able to grow in very dry environments.
Xerophiles
76
Aerobes-
Require oxygen to live
77
Anaerobes-
Do not require oxygen and may even be killed by exposure
78
Facultative organisms-
Can live with or without oxygen
79
Aerotolerant anaerobes-
Can tolerate oxygen to grow in its presence even though they cannot use it
80
Microaerophiles-
Can use oxygen only when it is present at levels reduced from that in air
81
___ are organisms that require oxygen to live.
Aerobes
82
___ are organisms that do not require oxygen and may even be killed by exposure.
Anaerobes
83
___ ___ are organisms that can live with or without oxygen.
Facultative organisms
84
___ ___ are organisms that can tolerate oxygen and grow in its presence even though they cannot use it.
Aerotolerant anaerobes
85
___ are organisms that can use oxygen only when it is present at levels reduced from that in air.
Microaerophiles
86
Thioglycolate broth-
Complex medium that separates microbes based on oxygen requirements
Reacts with oxygen, so oxygen can penetrate only the top of the tube
87
Reducing agents-
Chemicals that may be added to culture media to reduce oxygen
88
Several toxic forms of oxygen can be formed in the cell:
- single oxygen
- superoxide anion
- hydrogen peroxide
- hydroxyl radical
89
Sterilization-
The killing or removal of all viable organisms within a growth medium
90
Inhibition-
Effectively limiting microbial growth
91
Decontamination-
The treatment of an object to make it safe to handle
92
Disinfection-
Directly targets the removal of all pathogens, not necessarily all microorganisms
93
___ is the killing or removal of all viable organisms within a growth medium.
Sterilization
94
___ is effectively limiting microbial growth.
Inhibition
95
___ is the treatment of an object to make it safe to handle.
Decontamination
96
___ directly targets the removal of all pathogens, not necessarily all microorganisms.
Disinfection
97
Heat sterilization-
Most widely used method of controlling microbial growth
98
What is the most widely used method of controlling microbial growth?
Heat sterilization
99
High temperatures ___ macromolecules.
Denature
100
Decimal reduction time-
Amount of time required to reduce viability tenfold
101
Amount of time required to reduce viability tenfold is called the ___ ___ ___.
Decimal reduction time
102
Some bacteria produce resistant cells called ___.
Endospores
103
The ___ is a sealed device that uses steam under pressure.
Autoclave
104
Autoclave-
A sealed device that uses steam under pressure
105
Autoclave allows temperature of water to get above ___.
100C
106
What kills the microbes in the autoclave?
The high temperature
107
Pasteurization-
The process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids
108
___ is the process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids.
Pasteurization
109
Microwaves, UV, x-rays, gamma rays, and electrons can reduce ___ ___.
Microbial growth
110
___ has sufficient energy to cause modifications and breaks in DNA.
UV
111
UV is useful for what?
Decontaminating surfaces
112
___ cannot penetrate solid, opaque, or light-absorbing surfaces.
UV
113
Ionizing radiation-
Electromagnetic radiation that produces ions and other reactive molecules
114
Ionizing radiation generates what?
Electrons, hydroxyl radicals, and hydride radicals
115
Sources of ___ include cathode ray tubes, x-rays, and radioactive nuclides.
Radiation
116
___ is used for sterilization in the medical field and food industry.
Radiation
117
___ avoids the use of heat on sensitive liquids and gases.
Filtration
118
Depth filters-
HEPA filters
119
Membrane filters-
Function more like a sieve
Filtration can be accomplished by syringe, pump, or vacuum
120
Antimicrobial agents can be classified as ___, ___, and ___.
Bacteriostatic
Bacteriocidal
Bacteriolytic
121
Minimum inhibitory concentration (MIC)-
The smallest amount of an agent needed to inhibit growth or an organism
122
Disc diffusion assay-
Uses solid media
Antimicrobial agent added to filter paper disc
123
Zone of inhibition-
Area of no growth around disc
