Mesophiles are microorganisms that grow optimally at moderate temperatures, typically between about 20 °C and 45 °C, with most human pathogens preferring around 37 °C.
Explanation
Temperature influences enzyme kinetics, membrane fluidity and overall metabolic activity. Mesophilic organisms have evolved to thrive at intermediate temperatures common in temperate climates and within warm‑blooded hosts. Their enzymes function efficiently near body temperature and denature at extremes. The mesophilic range is typically defined as 20–45 °C, with an optimum around 37 °C for many bacteria associated with humans and animals. Organisms below this range are psychrophiles, while those above 45 °C are thermophiles or hyperthermophiles. Mesophiles include the majority of medically important bacteria such as Escherichia coli, Staphylococcus aureus and Salmonella enterica. Fungi and many soil and aquatic microbes are also mesophilic, contributing to decomposition and nutrient cycling. Because their growth overlaps typical environmental temperatures, mesophiles are involved in spoilage of food at room temperature and in fermentation processes. Some mesophiles can tolerate short periods of higher or lower temperatures but cannot reproduce outside their optimum range. Understanding thermal preferences aids in designing culture conditions, controlling microbial growth in food and environmental systems, and interpreting ecological distributions.
Examples and Relevance
- Common mesophilic bacteria: Escherichia coli, Streptococcus pyogenes, Salmonella enterica, Staphylococcus aureus, Bacillus subtilis.
- Mesophilic fungi and yeasts play roles in bread baking, beer brewing and cheese production.
- Soil mesophiles decompose organic matter and contribute to nutrient recycling in agriculture.
- Control of mesophilic pathogens is a major focus of pasteurization and refrigeration practices in food safety.
Mesophilic microorganisms dominate temperate ecosystems and the microbiota of humans and animals. Knowing their temperature preferences helps microbiologists cultivate them effectively and design strategies to promote beneficial fermentation or prevent spoilage and disease.
Related Terms: Psychrophile, Thermophile, Homeostasis, Temperature Range, Optimal Growth