environmental requirements for growth Flashcards
list 6 factors that affect growth of microbes
pH, temperature, oxygen, solutes/water activity, pressure, radiation
what is the formula for pH
pH = -log[H+]
M of H+ at pH=0?
1 M
M of H+ at pH=14?
1 x 10^-14
what pH range do neutrophiles like
5.5-8.0
what pH range do acidophiles like
0.0-5.5
what pH range do alkaliphiles like
8.0-11.5
T or F: bacteria can adapt to environmental pH changes in order to survive
true
what is the role of acid shock proteins
protect bacteria when there’s acidity by preventing protein denaturation
how do acid shock proteins work
if the environment becomes acidic, then the bacteria will produce these proteins which help prevent protein denaturation + they can make use of proton pumps
what are the cardinal temperatures
minimum, optimum, and maximum
what is the minimum temperature for a bacteria
lowest temp at which the species will grow
what is the optimum temp for a bacteria
where the bacteria grows best
what is the maximum temp for a bacteria
the highest temp at which the bacteria will grow
is the optimum temp closer to the min or the max temp
closer to the max
what is the max temp for prokaryotes
121 C
why can’t bacteria grow below their min temp
membrane gelling will occur = transport processes are so slow that growth cannot occur
why does bacterial growth rate increase as the temp increases
enzymatic reactions are occurring at increasingly rapid rates
describe enzymatic reactions at the optimum temp
they’re occurring at the maximal possible rate
why can’t bacteria grow beyond their max temp
protein denaturation occurs, cytoplasmic membrane collapses, thermal lysis occurs
what is the general growth range for bacteria
30-40 C
list the 5 classes of organisms based on their temp ranges for growth
psychrophiles, psychrotrophs, mesophiles, thermophiles, hyperthermophiles
where are psychrophiles found
in the ocean depths or in arctic/Antarctic habitats, and in snow fields
what adaptations do psychrophiles have that allow them to survive in low temps
high levels of unsat FAs in PM, they contain antifreeze proteins which bind to ice crystals + prevent them from getting larger so they don’t pierce the PM and kill the organism
what are psychrotrophs important for
important in the spoilage of food
which class of bacteria based on temp range is the most common
mesophile
which class of bacteria based on temp range do all human pathogens fall under
mesophiles
where can thermophiles be found
organic compost piles, hot water lines, hot springs
what type of organism are thermophiles (ie pro or eu)
prokaryotic, but there are some algae and fungi
why are thermophiles important
this is where we get heat resistant enzymes from by isolating the DNA for PCR
where are hyperthermophiles found
in deep sea hydrothermal vents or hot springs associated with volcanic activity
how do hyperthermophiles adapt to such high temps
have heat-stable enzymes and protein synthesis systems that prevent denaturation. Proteins have lots of proline = makes enzymes more stable at high temps. Proteins have lots of H bonding. They have NAPS to help stabilize DNA (ie histones). Proteins may be stabilized by chaperones. FAs = saturated = tight packing = less fluid at high temps. Lipids are more branched, use ether linkages, and some have monolayers
what are the two groups of bacteria based on oxygen requirements
aerobes or anerobes
what are the 2 types of aerobes
obligate aerobes and microaerophiles
what are the 3 types of anaerobes
facultative anaerobe, aerotolerant anaerobe, and strict/obligate anaerobe
describe the oxygen needs of obligate aerobes
requires oxygen
how do we culture obligate aerobes
make use of a shaking incubator to give them lots of O2
describe oxygen needs of microaerophiles
requires O2 to grow, but at lower levels than atmospheric level (2-10% vs 20%)
how do we grow microaerophiles
use a CO2 generating packet to reduce O2 levels
describe oxygen requirements for facultative anaerobes
does not require O2 for growth, but grows better when its present
how do we grow facultative anaerobes
make use of a shaking incubator
describe the oxygen requirements for aerotolerant anaerobes
O2 has no effect on growth. It grows equally in presence or absence
describe the oxygen requirements for strict/obligate anaerobes
does not grow in the presence of O2
how do we test for aerotolerance
make use of a eugon agar deep. Put the organism in, roll to mix, let harden overnight, then observe the growth
describe the growth pattern within a eugon agar deep of an obligate aerobe
growth at the top
describe the growth pattern within a eugon agar deep of a facultative anaerobe
growth at the top and a bit throughout
describe the growth pattern within a eugon agar deep of an aerotolerant anaerobe
growth throughout
describe the growth pattern within a eugon agar deep of an obligate anaerobe
growth at the bottom
describe the growth pattern within a eugon agar deep of a microaerophile
growth just below the surface layer
T or F: obligate anaerobes exposed to oxygen will die
true
T or F: atmospheric oxygen + oxygen in chemical compounds is toxic to obligate anaerobes
false; these are not the forms of oxygen that are toxic
what forms of oxygen are toxic to obligate anaerobes
singlet oxygen, superoxide radical, peroxide anion, and hydroxyl radical
what is the name for the toxic forms of oxygen
Reactive Oxygen Species (ROS)
what does ROS stand for
reactive oxygen species
why are ROS toxic
they’re strong oxidizing agents and cause damage by oxidizing important compounds within the cell
how is toxic oxygen produced
by ionizing radiation (ie gamma) or through normal metabolic reactions of bacteria
name the two enzymes that protect microbes from toxic forms of oxygen
superoxide dismutase (SOD) and catalase
what reaction does superoxide dismutase do
2 O2- + 2 H+ –> H2O2 + O2
in the SOD reaction, 2 O2- + 2 H+ → H2O2 + O2, which part is toxic
peroxide ion: O2^2-
what reaction does catalase do
2 H2O2 –> 2 H2O + O2
how is water availability expressed
expressed as water activity, with the abbreviation aw
what is the aw value for distilled water
1
what aw value do most microbes require to grow well
aw = 0.98
what occurs to the cell in a hypertonic environment
bacteria = plasmolyzed (water rushes out and PM pulls away from the cell wall)
what is an osmophile
prefers to live in a hypertonic environment
what solute type do osmophiles like
organic solutes like sugar or yeast (not things like salt)
what is a halophile
an organism that requires NaCl at a concentration more than 0.2 M
what concentration (minimum) of NaCl do halophiles need
more than 0.2 M
T or F: osmophiles like salt
false; they only like organic solutes like sugar or yeast
T or F: halophiles like salt (NaCl)
true
what salt concentration range do extreme halophiles require
3-6.2 M
what is a halotolerant organism
can grow in a wide range of NaCl concentrations
what type of medium (in cell culturing) can be used for plating organisms with high salt tolerances
MSA: contains high salt concentration = selective medium
what is a compatible solute
a molecule that doesn’t interfere with metabolism or growth when present at high intracellular concentrations
why would microbes want to use compatible solutes
they accumulate to make the internal solute concentration higher than the external concentration, and this prevents water loss and instead water moves in
what type of environment would cells want to have compatible solutes
hypertonic; bc compatible solutes prevent water loss
where can cells get compatible solutes
they can produce them or get them from the environment
give 4 examples of compatible solutes
KCl, choline, proline, glutamic acid
what are KCl, proline, choline, and glutamic acid examples of
compatible solutes
what would cells use to prevent the inward flow of too much water
mechanosensitive channels
where are mechanosensitive channels located
in the PM
describe how mechanosensitive channels work
they prevent the build up of pressure as water moves into the cell via channel opening and releasing solute
what is the atmospheric pressure at sea level
1 atm
what are barotolerant organisms
can withstand high pressure
what are barophilic organisms
grows optimally at pressure greater than 1 atm
1 atm = x pounds per square inch
14.7
list 2 membrane adaptations to high pressure
more unsaturated fatty acids, length of fatty acids may shorten
what is the major form of radion on earth
the sun
what types of light do we get from the sun
UV, visible, infrared, and radio
which type of light is responsible for heating the earth
infrared
which type of light is used in photosynthesis
visible
which type of light is dangerous + why
UV: as the wavelength decreases, the energy increases
how can visible light cause damage to microbes
it can damage or kill microbial cells when present in sufficient intensity. Bacteria contain pigments that can absorb he light energy and produce singlet oxygen (toxic)
which form of toxic oxygen can bacteria produce when they absorb light energy
singlet oxyegn
how do airborne bacteria + bacteria on exposed surfaces protect themselves from light?
they have carotenoid pigments that absorb energy from singlet oxygen, thereby preventing its toxic effects
