Psychrotrophic microbes are able to grow at temperatures below , but have better growth rates at higher temperatures. Psychrotrophic bacteria and fungi are able to grow at refrigeration temperatures, and can be responsible for food spoilage and as foodborne pathogens such as Yersinia. They provide an estimation of the product's shelf life, but also they can be found in soils, in surface and deep sea waters, in Antarctic ecosystems, and in foods.
Psychrotrophic bacteria are of particular concern to the dairy industry. Most are killed by pasteurization; however, they can be present in milk as post-pasteurization contaminants due to less than adequate sanitation practices. According to the Food Science Department at Cornell University, psychrotrophs are bacteria capable of growth at temperatures at or less than . At freezing temperatures, growth of psychrotrophic bacteria becomes negligible or virtually stops.
All three subunits of the RecBCD enzyme are essential for physiological activities of the enzyme in the Antarctic Pseudomonas syringae, namely, repairing of DNA damage and supporting the growth at low temperature. The RecBCD enzymes are exchangeable between the psychrophilic P. syringae and the mesophilic E. coli when provided with the entire protein complex from same species. However, the RecBC proteins (RecBCPs and RecBCEc) of the two bacteria are not equivalent; the RecBCEc is proficient in DNA recombination and repair, and supports the growth of P. syringae at low temperature, while RecBCPs is insufficient for these functions. Finally, both helicase and nuclease activity of the RecBCDPs are although important for DNA repair and growth of P. syringae at low temperature, the RecB-nuclease activity is not essential in vivo.