Download Bacterial Nutrition & Growth

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts
no text concepts found
Transcript
Environmental Factors
Tolerance to All Environmental Factors
(Shelford’s Law of Tolerance)
•
•
•
•
•
•
Temperature
Solute Concentration / Water Activity
pH (acidity versus alkalinity)
Oxygen Concentration
Barometric Pressure
Electromagnetic Radiation
Cardinal Temperatures
Minimum, Optimum, and Maximum
Growth:
An average day in
your ‘frig.
None
Slow
Rapid
Slow
Psychrotrophs
None
Food items cool more
rapidly in a shallow
container due to greater
surface to volume ratio.
Water Activity
Quantifies water availability in an environment;
decreases with increasing solute concentration.
Plasmolysis: hypertonic solutions; cytoplasm water loss; compatible solutes.
Osmotolerant: grows over a wide range of water activity; fungi > bacteria.
Halophile: “salt-loving”; requires > 0.2M sodium chloride.
• All prokaryotes
begin to die at
intracellular pH < 5.
•Neutrophiles:
(5.5 -8.0); swap
protons for K+.
•Alkalophiles:
(8.5-10.5); swap
protons for Na+;
buffer compounds
in cytoplasm.
•Acidophiles:
(0-5.5): extreme
control over
generating ATP.
Oxygen Requirement Types
2 to 10% atm O2
Super Oxide Dismutase (SOD): superoxide radicals go to hydrogen peroxide & O2.
Catalase: hydrogen peroxide go to water & O2.
Barometric Pressure
Barotolerant versus Barophiles
Membranes are very fluid
(=unsatuated short-chain fatty acids)
Electromagnetic Radiation
• Shorter wavelengths are
higher energy.
• Ionizing radiation:
Gamma & X-Rays; OH·;
sterilizing plastics.
• Ultraviolet radiation:
DNA damage at 265nm;
sterilizing surfaces &
water treatment.
• Visible light (PAR):
photosynthetic energy;
bacterial pigments get
excited; transfer energy
to O2 to form singlet
oxygen; cell damage.