mesophiles

Mesophiles are microorganisms that grow best at moderate temperatures. Their growth range generally spans from about 20°C to 45°C, with many species reaching optimal growth near 25–37°C. This group includes a large portion of bacteria that inhabit warm-blooded animals and terrestrial and aquatic environments, as well as numerous yeasts and molds.

Habitats for mesophiles are diverse, including soil, water, decaying organic matter, and host-associated communities. In medical and food contexts, mesophiles are particularly relevant because human pathogens and many spoilage organisms fall within this temperature range. For example, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Saccharomyces cerevisiae are commonly cited mesophiles.

Physiological characteristics of mesophiles reflect adaptation to moderate temperatures. Their enzymes and cellular processes function best at these temperatures, and membrane lipid composition often balances fluidity and stability within the mesophilic range. When exposed to temperatures outside their optimum, mesophiles may experience slowed growth or stress responses, including the production of heat-shock or cold-adaptation proteins.

Relation to other temperature classes is a key aspect of microbiology. Psychrophiles prefer cold environments and have optimum growth below 15°C, while thermophiles thrive at higher temperatures above about 45°C. Mesophiles thus occupy a middle ground that aligns with many natural habitats and human-associated settings.

Understanding mesophiles is important for food safety, clinical microbiology, and biotechnological applications, where temperature control influences growth, preservation, and product development.