Psychrophiles or cryophiles (adj. cryophilic) are extremophilic organisms that are capable of growth and reproduction in cold temperatures, ranging from −20 °C to +10 °C. Temperatures as low as −15 °C are found in pockets of very salty water (brine) surrounded by sea ice. Psychrophiles are true extremophiles because they adapt not only to low temperatures but often also to further environmental constraints. They can be contrasted with thermophiles, which thrive at unusually hot temperatures. In addition to that, distinctions between mesophilic and psychrophilic cold-shock response, including lack of repression of house-keeping protein synthesis and the presence of cold-acclimation proteins (Caps) in psychrophiles, does exist. The environments they inhabit are ubiquitous on Earth, as a larg