A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from .[Willey, Joanne M., Linda Sherwood, Christopher J. Woolverton, and Lansing M. Prescott. Prescott, Harley, and Klein's Microbiology. New York: McGraw-Hill Higher Education, 2008. Print.] The optimum growth temperature for these organisms is 37 °C (about 99 °F).
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
celsius, 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 that prefer cold environments are termed
psychrophile, those preferring warmer temperatures are termed
Thermophile and those thriving in extremely hot environments are
hyperthermophile.
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 (
alleles) 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.[Vijayabaskar, Mahalingam S. et al. "Construction of Energy Based Protein Structure Networks: Application in the Comparative Analysis of Thermophiles and Mesophiles" Biophysical Journal, Volume 98, Issue 3, 387a] 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.[Perrot, F., Hébraud, M., Junter, G.-A. and Jouenne, T. "Protein synthesis in Escherichia coli at 4°C. Electrophoresis." 2000, 21: 1625–1629. doi:10.1002/(SICI)1522-2683(20000501)21:8<1625::AID-ELPS1625>3.0.CO;2-4] Oxygen availability also affects microorganism growth.[Sinclair, N. A.; Stokes, J. L. " ROLE OF OXYGEN IN THE HIGH CELL YIELDS OF PSYCHROPHILES AND MESOPHILES AT LOW TEMPERATURES." The Journal of Bacteriology, 1963, Vol. 85(1), p.164 Peer]
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.
Oxygen requirements
Due to the diversity of mesophiles, oxygen requirements greatly vary. Aerobic respiration requires the use of
oxygen and anaerobic does not. There are three types of
anaerobes. Facultative anaerobes grow in the absence of oxygen, using
fermentation instead. During fermentation, sugars are converted to
acids,
ethanol, or
. If there is oxygen present, it will use aerobic respiration instead. Obligate anaerobes cannot grow in the presence of oxygen. Aerotolerant anaerobes can withstand oxygen.
Roles
Microorganisms play an important role in
decomposition of organic matter and mineralization of
nutrients. In aquatic environments, the diversity of the
ecosystem allows for the diversity of mesophiles. The functions of each mesophile rely on the surroundings, most importantly temperature range.
[Ferroni, G.D., Kaminski, J.S. "Psychrophiles, psychrotrophs, and mesophiles in an environment which experiences seasonal temperature fluctuations." Canadian Journal of Microbiology, 1980, 26:1184-1191, 10.1139/m80-198] Bacteria such as mesophiles and
are used in the
cheesemaking due to their role in
fermentation. "Traditional
use the following terms to indicate the general (slightly arbitrary) optimum temperature for the growth of bacteria:
(15–20 °C), mesophiles (30–37 °C), thermophiles (50–60 °C) and extreme thermophiles (up to 122 °C)".
[Johnson, Mark. "Mesophilic and Thermophilic Cultures Used in Traditional Cheesemaking." Cheese and Microbes. Washington: ASM Publishing. 2014. Web.] Both mesophiles and thermophiles are used in cheesemaking for the same reason; however, they grow, thrive and die at different temperatures. Psychrotrophic bacteria contribute to dairy products spoiling, getting mouldy or going bad due to their ability to grow at lower temperatures such as in a refrigerator.
Examples
Some notable mesophiles include
Listeria monocytogenes,
Staphylococcus aureus, and
Escherichia coli. Other examples of
species of mesophiles are
Clostridium kluyveri,
Pseudomonas maltophilia,
Thiobacillus novellus,
Streptococcus pyogenes, and
Streptococcus pneumoniae. Different types of diseases and infections typically have pathogens from mesophilic bacteria such as the ones listed above.
Listeria monocytogenes
Listeria monocytogenes is a gram-positive bacterium. It is closely related to
Bacillus and
Staphylococcus. It is a rod-shaped, facultative anaerobe that is motile by peritrichous
flagella.
L. monocytogenes motility is limited from 20 °C to 25 °C.
[ At the optimal temperature, it loses its motility. This bacterium is responsible for listeriosis which derives from contaminated food.][Magalhã£Es, R. (2014). Listeria monocytogenes. 450-461.
]
Staphylococcus aureus
Staphylococcus aureus was first identified in 1880.[ It is responsible for different infections stemming from an injury. The bacterium overcomes the body's natural mechanisms. Long lasting infections of S. aureus includes pneumonia, meningitis, and osteomyelitis. S. aureus is commonly contracted in hospital settings.][Todd, E. (2014). Staphylococcus Aureus. 530-534]
Escherichia coli
Escherichia coli is a gram-negative, rod-shaped facultative anaerobic bacterium that does not produce spores.[ The bacterium is a member of Enterobacteriaceae. It is capable of producing enterotoxins which are thermolabile or thermostable.][Robinson, Richard K.. (2000). Encyclopedia of Food Microbiology, Volumes 1-3 - Escherichia Coli. Elsevier. Online version available at: http://app.knovel.com/hotlink/pdf/id:kt0051LGG3/encyclopedia-food-microbiology/escherichia-coli] Other characteristics of E. coli are that it is oxidase-negative, citrate-negative, methyl red positive, and Voges-Proskauer-negative. To sum up E. coli, it is a coliform. It is able to use glucose and acetate as a carbon source for fermentation. E. coli is commonly found in the Digestive system of living organisms.[ E. coli has many capabilities such as being a host for recombinant DNA and being a pathogen.][Robinson, Richard K.. (2000). Encyclopedia of Food Microbiology, Volumes 1-3 - Escherichia Coli. Elsevier. Online version available at: http://app.knovel.com/hotlink/pdf/id:kt0051K7I1/encyclopedia-food-microbiology/ecology-bacteria-escherichia-3]
See also
