Mesofiilit

In microbiology, mesofiilit (also called mesophiles) are organisms that grow best at moderate temperatures. The name combines Greek roots mesos “middle” and philos “loving.” Mesophiles form a middle category between psychrophiles (cold-loving) and thermophiles (heat-loving).

Temperature range: Most mesophiles prefer growth temperatures between about 20°C and 45°C, with many thriving near 30–37°C. The human body’s temperature, around 37°C, supports a large portion of mesophilic organisms, including many pathogens. Some sources tighten the core range to roughly 25–40°C. Growth outside these temperatures is slower and can be lethal for some species.

Habitats and significance: Mesophiles are widespread in soil, freshwater and marine environments, decaying organic matter, plants and animals, and in food products. They include bacteria, yeasts and many filamentous fungi. Notable examples include Escherichia coli, Staphylococcus aureus and Bacillus subtilis, as well as Saccharomyces cerevisiae. While many mesophiles are harmless, others are important human pathogens or spoilage agents. In industry, mesophiles are used in fermentation and biotechnology processes conducted at moderate temperatures.

Physiology: Enzymes and cellular processes in mesophiles are adapted to function efficiently at intermediate temperatures. They often lack the specialized heat-stable proteins and membrane lipids seen in thermophiles, and they may produce heat shock proteins in response to sudden temperature increases. Their growth is influenced by pH, salinity, and nutrient availability, but their optimum temperatures remain moderate.