psychrotolerant

Psychrotolerant refers to microorganisms that can grow at low temperatures, including near 0°C, but prefer and thrive at warmer temperatures. These organisms have an upper temperature limit for growth that is typically well above the range in which true psychrophiles dominate, and they may grow over a broad temperature range from near freezing to moderate warmth. In practice, psychrotolerant (or psychrotrophic) organisms can grow at 0°C or close to it, with optimal growth commonly in the range of 15–25°C and maximum growth up to around 30–35°C, depending on the species.

Psychrotolerant microbes are found in diverse environments, including soil, freshwater, and marine ecosystems, as well as in refrigerated foods and processed products. They are of particular relevance in food microbiology because their ability to grow at refrigeration temperatures contributes to spoilage and, in some cases, foodborne illness. Notable examples include certain bacteria such as Listeria monocytogenes, Pseudomonas species, and some Bacillus strains, as well as various yeasts and molds.

Adaptations that enable cold tolerance involve changes in cell membrane composition to maintain fluidity at low temperatures, production of cold-adaptive enzymes, and the accumulation of compatible solutes and cold-shock proteins. These mechanisms help organisms sustain metabolism, replication, and stress responses in cold environments.

Understanding psychrotolerant microbes informs food safety practices, including proper refrigeration, sanitation, and monitoring, to limit spoilage and pathogen risk in refrigerated products and in environments where cold temperatures prevail.