Psychrotrophic

Psychrotrophic refers to microorganisms that can grow at low temperatures, including refrigeration temperatures, but whose optimal growth temperature is above 15°C. They typically grow from roughly 0°C to about 30–35°C, with an optimum around 20–30°C. They can multiply at 0°C in some cases and are commonly associated with cold environments and refrigerated foods.

Psychrotrophs differ from psychrophiles, which have their optimum growth at cold temperatures (often below 15°C). They are also distinct from mesophiles, which prefer moderate temperatures. Psychrotrophs are widespread in soil, water, and plant ecosystems and are important in food spoilage, as many can proliferate during storage of milk, meat, and seafood.

Physiological adaptations include cold-active enzymes, changes in membrane lipid composition with higher unsaturated fatty acids, production of cold-shock proteins and chaperones, and accumulation of compatible solutes that act as cryoprotectants. These features enable growth at low temperatures and survival during freezing.

Economically and clinically relevant psychrotrophs include Listeria monocytogenes and many Pseudomonas species, among others. They pose challenges for food safety and shelf life because they can grow at refrigeration temperatures. Control measures focus on rapid cooling, proper sanitation, and limiting time in the temperature danger zone.