Environmental Factors: Aeration and Osmotic Pressure

Aerobic

The organism uses oxygen

Anaerobic

the organism not using oxygen

obligate aerobes

microbial species requiring oxygen as hydrogen acceptor

facultative anaerobes

microbial species able to live aerobically or anaerobically, catalase and superoxide dismutase

microaerophiles

microbial species requiring small amounts of oxygen (2 – 10%), small amounts of catalase and superoxide dismutase

obligate anaerobes

microbial species requiring a substance other than oxygen as hydrogen acceptor and are sensitive to oxygen inhibition, neither catalase nor superoxide dismutase in most

aerotolerant anaerobes

• Indifferent to oxygen;

• can grow in its presence, but they do not use it as a hydrogen acceptor, superoxide dismutase

Aerobic Metabolism

The natural by-products are the reactive compounds hydrogen peroxide (H2O2) and superoxide (O2-).

Catalase

2H2O2 → 2H2O + O2

Superoxide Dismutase

2O2- + 2H+ → O2 + H2O2

Halophiles

• 15% microbes requiring NaCl (salt lovers)

• Capable of growing in high concentrations of salts

halotolerant

microbes tolerating NaCl

non-halophiles

microbes not tolerating NaCl

extreme halophiles

microbes requiring NaCl at 15% - 30%

Osmophiles

Capable of growing in high concentrations of sugars

plasmolysis

osmotic loss of water

plasmolyzed cell in hypertonic solution

• high solute of concentration

• shrink

moderate

3% - 15% sea water

extreme

15% - 30% dead sea