Permanently cold environments are widely distributed
on Earth, and include the Polar Regions, mountains and
deep-sea environments.Despite presenting adverse conditions
for life, such as freezing temperatures, low nutrient
availability, high water viscosity and reduced
membrane fluidity, these environments have been successfully
colonized by the three domains of life.Cold-adapted microorganisms can grow at 0°C and are
classified as psychrophilic if their optimum and maximum
temperatures for growth are ≤15°C and ≤ 20, respectively,
or as psychrotolerant (psychrotrophic) if their
maximum temperature for growth is above 20°C.Such microorganisms have adapted their vital cellular
processes to thrive in cold environments.