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microbiology 319 > chapter 9 microbial growth > Flashcards

chapter 9 microbial growth Flashcards

exam 2 (65 cards)

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1
Q

N2 makes up nearly

A

79% of the earth’s atmosphere
but the nitrogen in N2 is unavailable for use by most organisms

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2
Q

nitrogen must be fixed to

A

ammonium ions (NH4) through the nitrogen cycle

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3
Q

the nitrogen cycle

A
  1. nitrogen is removed from the air and converted to ammonia (ex Rhizobium- nitrogen fixer)
  2. Ammonia is converted to nitrate (nitrifiers)
  3. Nitrogen is removed from ammonia and converted to Nitrogen gas (denitrifiers)
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4
Q

most bacteria grow by

A

binary fission
one parent cell splits into two equal daughter cells
bacteria have no nucleus and divide very rapidly

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5
Q

what is crucial for the development of the septum in bacterial cell division

A

FtsZ ring

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6
Q

what does the FtsZ ring do

A

assembles itself at the septum to help the development of the septum
the septum is necessary for the split of the 2 daughter cells
pinches cytoplasm

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7
Q

budding

A

new daughter cell forms as a small outgrowth (bud) from the parent (mother) cell.
the offspring is small at first and later grows

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8
Q

batch culture system

A

closed system used to grow microorganisms in a fixed volume of nutrient-rich medium without adding or removing anything once the culture begins

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9
Q

growth curve of a culture

A
  1. lag phase
  2. log phase
  3. stationary phase
  4. death or decline phase
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10
Q

lag phase

A

no increase in the number of living bacterial cells

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11
Q

log phase

A

exponential increase in number of living bacterial cells
dividing very rapidly

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12
Q

stationary phase

A

-plateau in the number of living bacterial cells
-rate of cell division and cell death are equal
-occurs when running out of nutrients and build-up of waste products

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13
Q

death or decline phase

A

exponential decrease in the number of living bacterial cells

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14
Q

formula for number of cells after a particular generation

A

1 x 2
the exponent on top of 2 is whatever generation ur interested in

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15
Q

continuous culture system

A

fresh medium is continually added to a culture and an equal amount of culture is constantly siphoned off
bacterial populations can be kept in exponential growth for a long time

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16
Q

biofilms

A

complex and dynamic ecosystems that commonly form on surfaces

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17
Q

biofilm growth

A
  1. cellular flagella attach to the monolayer
  2. microcolonies form
  3. cells produce EPSs (cover the cells)
  4. biofilm matures
  5. biofilm dissolves and cells disperse
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18
Q

physical requirements for growth

A
  1. pH
  2. temperature
  3. moisture
  4. hydrostatic pressure
  5. osmotic pressure
  6. radiation
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19
Q

chemical requirements for growth

A
  1. carbon
  2. nitrogen
  3. sulfur
  4. phosphorus
  5. trace elements
  6. organic compounds
  7. oxygen
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20
Q

low temperature-growing bacteria

A

psychrophiles
psychotroph

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21
Q

psychotroph

A

grows at low temps
optimal temp: 20-30 C but can grow in temps as low as 0 C
food spoilage bacteria

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22
Q

psychrophile

A

optimal temp: 10 C
growth range: -5C - 20 C

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23
Q

mesophiles

A

optimal temp: 30 C
range: 15 C- 45C

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24
Q

thermophiles

A

optimal temp: 60 C
range: 40 C - 80 C

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25
hyperthermophiles
optimal temp: 90 C range: 65 C - 105 C
26
organisms that adapted to grow at high pressure
barophiles (weight loving) piezophiles (pressure loving)
27
the more particles in a solution the
greater the osmolarity and the lower the water activity
28
water activity
measure of water availability the more solutes in a solution the less water is available for microbes to use for growth
29
osmolarity
measure of the number of solute molecules in a solution
30
halophiles
only grow in high-salt environments
31
plasmolysis
caused by hypertonic environments or an increase in salt or sugar the cell begins to shrink bc it is dehydrated: water has moved out
32
extreme/ obligate halophiles
require high osmotic pressure need high salt concentration
33
facultative halophiles
tolerate high osmotic pressure can survive in high or low salt concentrations
34
acidophiles
exist in high acidic pH
35
alkaliphiles
exist in high basic pH 9-11
36
how does pH influence bacterial growth
altering protein shape which in turn changes protein activity
37
neutralophiles
bacteria that generally grow between 5-8 pH and include most human pathogens
38
aerobes
use oxygen as a terminal electron acceptor in the electron transport chain
39
anaerobes
oxygen is toxic
40
anaerobic respiration
electron transport systems without oxygen as terminal electron acceptor (nitrate)
41
facultative anaerobes
possess an enzyme to detoxify oxygen radicals and the machinery for fermentation and aerobic respiration
42
aerotolerant anaerobes
do not go through ETC just use fermentation tolerate oxygen: have enzymes to degrade O2 radicals ROS: reactive oxygen species
43
microaerophiles
grow only at low oxygen levels too much O2 is toxic
44
capnophiles
thrive in the presence of high carbon dioxide
45
enzymes that protect the cell from toxic oxygen
Hydrogen peroxide superoxide catalase superoxide dismutase
46
agar
complex polysaccharide solidifying agent for culture media not metabolized by microbes solidifies: 40 C liquifies: 100 C
47
selective media
encourage the growth of certain organisms and discourage the growth of others
48
differential media
enable different species to be distinguished from each other
49
enrichment media
encourage the growth of a specific organism fastidious microorganisms contains extra nutrients to allow organisms to grow
50
selective media
contains a growth-inhibiting additive which will limit growth on the medium to only those organisms that are desired
51
Mannitol salt agar
high concentrations of salt contains mannitol and phenol red selective: organisms that can grow w salt differential: can ferment mannitol
52
MacConkey Agar
crystal violet, neutral red and bile salts, and lactose selective: organisms that grow w bile salts differential: can ferment lactose
53
blood agar
differential media that distinguish species that can break down the red blood cells included in the blood agar medium
54
B hemolysis
completely lysed clear zone around colony
55
a hemolysis
partial degradation of RBC has a greenish color
56
y hemolysis
no degradation: colonies appear red
57
spread plate method
sample placed on top of agar AGAR IS PLACED FIRST
58
pour plate method
sample is placed first and then agar is mixed into it
59
viable cell count
the number of living cells in a sample
60
total cell count
the number of living and dead cells in a sample
61
turbidity
the degree to which the liquid medium has become cloudy because of microbial growth
62
preserving bacterial cultures
Deep freezing: -50 to -95 C lyophilization: frozen -54 to -72 C and dehydrated in a vacuum
63
fluorescence labeling
propidium iodide: unable to cross the cell mem of live/intact cells but can stain the nucleic acid of lysed cells red Syto 9 Green: membrane permeable and will bind to both live and dead cells LIVE CELLS GREEN DEAD RED
64
direct counting of bacteria without a microscope
fluorescence-activated cell sorter (FACS) count and separate bacterial cells with different properties
65
spectrophotometer
measures the amount of light absorption by a bacterial broth culture at a particular wavelength

microbiology 319 (16 decks)

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