Mesophile
A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from. The optimum growth temperature for these organisms is 37 °C. The term is mainly applied to microorganisms. Organisms that prefer extreme environments are known as extremophiles. Mesophiles have diverse classifications, belonging to two domains: Bacteria, Archaea, and to kingdom Fungi of domain Eukarya. Mesophiles belonging to the domain Bacteria can either be gram-positive or gram-negative. Oxygen requirements for mesophiles can be aerobic or anaerobic. There are three basic shapes of mesophiles: coccus, bacillus, and spiral.
Habitat
The habitats of mesophiles can include cheese and yogurt. They are often included during fermentation of beer and wine making. Since normal human body temperature is 37 °C, the majority of human pathogens are mesophiles, as are most of the organisms comprising the human microbiome.Mesophiles vs. extremophiles
Mesophiles are the opposite of extremophiles. Extremophiles that prefer cold environments are termed psychrophilic, those preferring warmer temperatures are termed thermophilic or thermotropic and those thriving in extremely hot environments are hyperthermophilic.A genome-wide computational approach has been designed by Zheng, et al. to classify bacteria into mesophilic and thermophilic.
Adaptations
All bacteria have their own optimum environmental surroundings and temperatures in which they thrive. Many factors are responsible for a given organism's optimal temperature range, but evidence suggests that the expression of particular genetic elements can alter the temperature-sensitive phenotype of the organism. A study published in 2016 demonstrated that mesophilic bacteria could be genetically engineered to express certain alleles from psychrophilic bacteria, consequently shifting the restrictive temperature range of the mesophilic bacteria to closely match that of the psychrophilic bacteria.Due to the less stable structure of mesophiles, it has reduced flexibility for protein synthesis. Mesophiles are not able to synthesize proteins in low temperatures. It is more sensitive to temperature changes, and the fatty acid composition of the membrane does not allow for much fluidity. Decreasing the optimal temperature of 37 °C to 0 °C to 8 °C leads to a gradual decrease in protein synthesis. Cold-induced proteins are induced during low temperatures, which then allows cold-shock proteins to synthesize. The shift back to the optimal temperature sees an increase, indicating that mesophiles are highly dependent on temperature. Oxygen availability also affects microorganism growth.
There are two explanations for thermophiles being able to survive at such high temperatures whereas mesophiles can not. The most evident explanation is that thermophiles are believed to have cell components that are relatively more stable than the cell components of mesophiles which is why thermophiles are able to live at higher temperatures than mesophiles. "A second school of thought, as represented by the writings of Gaughran and Allen, believes that rapid resynthesis of damaged or destroyed cell constituents is the key to the problem of biological stability to heat."