Table 1 Glossary

Psychrophile

Optimal growth temperature ≤ 15°C, maximum~

20°C, minimum ≥ 0°C

Psychrotroph

Can grow at or below 5°C, maximum 25°C - 30°C

Mesophile

Optimal growth temperature approx 37°C, often grows from 8°C or 10°C to 45°C or 50°C

Thermophile

Grows at > 50°C

Hyperthemophile

Grows at > 80°C

pH

Acidophile

Grows at pH < 2

Alkaliphile

Grows at pH > 10

Salinity

Halophile

Extreme halophiles (archaea) need 2.5 M - 5.0 M salt for growth. Moderate halophiles will grow in up to 15-20% NaCl

Oxygen tension

Aerobes

Grow in ≥ 21% oxygen (level present in air)

Anaerobes

Grow only in the absence of oxygen

Microanaerobes

Grow at low levels of oxygen (not in air)

Facultative anaerobes

Can grow aerobically or anaerobically

Hydrostatic pressure

Piezophiles

Obligate piezophiles do not grow at atmospheric pressure (1 atmosphere, 0.1 MPa). Piezotolerant bacteria grow at I atmosphere but will also grow at high pressures (up to 130 MPa)

Chemical extremes

Some bacteria are metal-tolerant, others can tolerate high levels of gases (e.g., carbon dioxide)