Microbial Growth Requirements Flashcards
what are 3 physical requirements for microbial growth
- temperature
- barometric pressure
- radiation
what are 3 biochemical requirements for microbial growth
- osmotic pressure (water)
- pH
- inorganic nutrients
what would be biochemical effects of being at a temperature below + above optimal
below
- membranes solidify
- metabolism slows
above
- membranes melt
- proteins denature
what are mesophilic bacteria
grow optimally at 37 °C
~ infect humans
what are thermophiles / hyperthermophiles
thermo - organisms that grow above 50 °C
hyper - grow at 100 °C (hydrothermal vents)
what adaptations allow for prokaryotes to survive at high temps
~ heat stable enzymes/proteins
~ less fluid membranes
bacteria
- longer, saturated FA tails
archaea
- have branched hydrocarbons
~monolayers
~ether bonds
what are psychrotrops vs psycrophiles
trops - organisms that grow around 5-7 °C (big concern for food safety)
philes - grow in extreme cold (-20 - 0 °C) * found in all permanently cold regions of the world
what adaptations allow microbes to grow at cold temperatures (3)
- raise osmotic pressure inside cell
- make antifreeze proteins
~ prevent water crystallization - have short, unsaturated fatty acids in membrane lipids (increase fluidity)
what organisms grow under high pressure and describe what adaptations they have
- barophilic / barotolerant
have:
- viscous membrane
- unsaturated lipids
what are radioresistant organisms
able to survive at higher levels of radiation
compare UV radiation vs Ionizing radiation
UV:
- absorbed by DNA and damages
Ionizing:
- changes structure / causes mutations in DNA
what are microbes called who prefer high osmotic pressure vs high salt conc
osmotic pressure - osmophiles
high salt - halophiles
*are all osmophiles as high salt conc causes high osmotic pressure
isotonic medium
- solute concentration of medium is same as cell interior
hypertonic medium
- higher solute concentration in medium compared to cell interior
~water leaves cell by osmosis
~looks shriveled
hypotonic medium
- lower solute concentration in medium compared to cell interior
~influx of water by osmosis
~membrane swells & and could causes lysis
how do freshwater bacteria adapt to low osmotic pressure
presence of cell wall
how to prokaryotes without cell walls adapt to low osmotic pressure
- large amounts of sterols (ex. hopanoids to stabilize membrane)
how do halophilic/osmophilic bacteria adapt to high osmotic pressure ?
increase intracellular compatible solutes
ex.
inorganic - KCI
organic - certain AA or sugars
what helps microbial eukaryotes regulate osmotic pressure
the contractile vacoule
~ pumps water in and out of cell
3 different types of pH organisms and what happens when they’re not in their ideal
neutrophiles - prefer neutral pH (5.5-8)
acidophiles - prefer acidic (0-5.5)
alkaliphiles - prefer basic (8-11.5)
not in ideal
- inactivate proteins
- disrupt membrane lipids
what adaptations allow acidophiles to grow at a low pH (3)
anything to maintain a neutral cytoplasmic pH
- use ATP to pump H out of cell
- pump H out in exchange for Na
- maintain high K in the cell
what adaptations allow alkaliphiles to grow at high pH
anything to maintain a neutral cytoplasmic pH
- pump H into cell in exchange for Na
- make enzymes that tolerate basic conditions
what are ROS + 3 examples
Reactive Oxygen Species
- highly reactive form of oxygen that can damage cells
ex.
~superoxide radical (O2-)
~hydrogen peroxide (H2O2)
~hydroxyl radical (OH-)
~peroxide anion (O2 2-)
how do cells protect themselves from ROS? (3)
have antioxidants like
(hydrogen peroxide)
- catalase
- peroxidase
(superoxide radical)
- superoxide dismutase / reductase
