The term mesophiles It is used to refer to organisms that reach their optimal development at temperatures ranging between 20 and 45 ° C. Although all organisms that grow in this temperature range are mesophilic, the term is used mainly to speak of microorganisms.
Living things can grow in a relatively small range of temperatures, ranging from -5 ° C to just over 80 ° C. Growth below -5 ° C is restricted due to freezing of the cytoplasm and other organic fluids.
Very high temperatures, on the other hand, restrict growth due to the thermolability of cellular proteins..
Mesophilic microorganisms are very diverse and can be prokaryotes or even belong to the Fungi kingdom of the Eucarya. However, the term is more commonly used for bacteria. The latter can be in the shape of a coconut, a bacillus or have a spiral shape.
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Prokaryotes can be classified into three groups depending on the growth interval where their development occurs: thermophiles, mesophiles, and psychrophiles..
Its optimum temperature range for growth is between 55 and 75 ° C, while its minimum temperature is never lower than 35 ° C.
Their optimal growth temperature is 30 to 45 ° C (20 - 50 ° C according to some authors) and they do not thrive below 10 ° C.
They can be facultative or obligate psychrophiles. In the case of facultative psychrophiles, their optimum temperature is the same as for mesophiles, but the minimum is close to 0 ° C. While the obliged ones have an optimum temperature of 15 to 18 ° C, a minimum temperature of 0 ° C and a maximum of 20 ° C.
Because it is a purely ecological and functional term, the variability in organisms that it includes is quite large and it is difficult to make generalizations. Perhaps the only characteristic in common is the temperature range in which they develop.
In the case of mesophilic bacteria, these can be Gram positive or Gram negative. There are also no limitations regarding the oxygen requirements for its metabolism, which can be aerobic, anaerobic or facultative. In terms of shape, they can be cocci, bacilli, or spiral shaped.
Even temperature, the factor that defines them, is not a strict tool to separate bacteria into groups, since not all bacteria can thrive in the entire temperature range that defines their group. Even the pH can affect the resistance of bacteria to temperature..
Another possible common characteristic among all of them may be the presence of peptidoglycans in their cell wall; but in the case of Gram positive ones, they have a thicker layer of peptidoglycans than Gram negative ones.
Mesophiles, as already indicated, are a type of bacteria, according to their optimal development temperature.
But since most bacteria belong to this group, it can be subdivided based on different criteria, such as the response to vital dyes (Gram + or Gram -) or their shape (cocci, bacilli, coccobacilli, spirilli and vibrios).
Because some mesophilic bacteria, under environmental conditions, can contaminate food and cause its decomposition, or diseases (if ingested), it is common then to speak of aerobic mesophiles. In this case, a subdivision would be made based on the oxygen requirements. In this way we would obtain the following groups:
Mesophilic bacteria that require oxygen for their metabolic processes.
Those that live and develop in environments lacking oxygen and at medium temperatures. Many of them perish, or do not thrive, in the presence of oxygen, while others (aerotolerant) can grow in the presence of oxygen, but do not use it for their vital processes.
Bacteria that live and develop indistinctly in anaerobic or aerobic environments; that is, they can live in the presence (and use it) or absence of oxygen.
Provided that the temperatures are adequate, mesophilic bacteria can be found in any habitat, be it marine waters, rivers, in soils, on other organisms, or inside these.
Since most warm-blooded organisms have a body temperature close to 35 ° C, the bacteria that live inside them are mesophilic. These bacteria can establish mutually beneficial symbiotic relationships with their hosts, or they can act as parasites causing various diseases.
The normal temperature of humans is 37 ° C, so the pathogenic bacteria that affect humans are mesophilic. Some of the most important Foodborne Illnesses (FADs) are due to mesophilic aerobic bacteria.
Due to this, one of the hygiene and safety measures followed in the food industry is the counting of this type of bacteria in food to determine whether or not they are suitable for consumption. Additionally, some bacteria that are not pathogenic under normal conditions may occasionally act as such (opportunistic pathogens).
Diseases caused by mesophiles can have different medical relevance, from self-limited diarrhea to fatal diseases, some of them of hospital origin.
Among the diseases caused by mesophiles are for example: bacterial diarrhea, endophthalmitis, meningitis, diphtheria, peritonitis, prostatitis, pneumonia and septicemia. Some species of mesophiles, additionally, can develop drug resistance, which complicates their treatment..
It is a Gram positive, facultative anaerobic bacillus, capable of moving thanks to the presence of peritrichous flagella. This bacterium is mesophilic; however, it is able to survive temperatures of 0 ° C. It is the cause of the disease known as listeriasis.
Among the manifestations of the disease are nausea, vomiting and diarrhea, which may be the only symptoms, or it can progress to sepsis, meningitis, pneumonia, and even cervical or intrauterine infections that cause spontaneous abortions in pregnant women..
Listeria monocytogenes can be acquired by contaminated food, such as raw or pasteurized milk, cheeses, ice cream, fresh and smoked fish, among others.
It is a Gram negative, mobile, catalase positive and oxidase negative bacterium. This mesophyll is found in practically any aquatic environment, as well as in the soil or living on plants..
It is an opportunistic pathogen that can cause, although infrequently, pneumonia, urinary tract or blood system infections in people with compromised immune systems. However, it is increasingly common in lung infections and in individuals with cystic fibrosis..
Stenotrophomonas maltophilia It is acquired in the hospital, mainly through the use of infected urinary catheters as well as mechanical ventilation tubes, suction catheters and endoscopes that are also infected.
Gram positive bacteria, non-spore forming and nonmotile. Additionally, it is aerotolerant and negative calasse. This coconut-shaped bacterium is an unusual component of the skin's bacterial flora and is usually pathogenic..
Its specific epithet (pyogenes) is due to the fact that it produces a series of infections that generate pus. Diseases caused by it include scarlet fever, strep throat, rheumatic fever, and rheumatic heart disease..
The bacteria can be transmitted in a number of ways, including breathing in respiratory particles from an infected person, contact with contaminated skin or objects, and through contaminated food..
It is a Gram-positive, facultative anaerobic, coconut-shaped bacterium, usually found in pairs (diplococcus). This bacterium, also known as pneumococcus, is nonmotile and does not form spores. It can be alpha or beta hemolytic in the presence or absence of oxygen, respectively.
It is the main cause of pneumonia, but it can also cause other diseases, including meningitis, sepsis, bronchitis, rhinitis, osteomyelitis, peritonitis, cellulitis and even brain access, among others.
This bacteria can reside in the skin, respiratory tract and nasal cavity of healthy people. However, in people with weakened or compromised immune systems, it can become pathogenic. The route of infection can be auto-inoculation or through breath drops from infected people..
It is a Gram positive, nonmotile, facultative anaerobic bacillus that does not produce spores. It is also characterized by having arabinose, galactose and mannose in its cell wall and by containing metachromatic granules.
It is the main causative agent of diphtheria, which can be pharyngeal, tonsillar, laryngeal, nasal or cutaneous. It can cause the appearance of a pseudomembrane in the affected area, which can lead to death due to airway obstruction.
The form of contagion is through particles from the breath of an infected person during respiration, and it can also occur through direct contact with secretions from skin lesions..
Gram-positive, mobile, aerobic and facultative anaerobic bacillus, sporulating in the presence of oxygen. It is a ubiquitous bacterium in all temperate zones of the world, being commonly found in soil, water and food.
This species is responsible for most foodborne illness outbreaks, such as fried rice syndrome and diarrhea. It can also cause other diseases such as endocarditis, chronic skin infections that are difficult to eradicate, and musculoskeletal infections.
The form of contagion is by eating contaminated and improperly handled food. Bacillus cereus is capable of forming heat resistant endospores.
In botany, it is called the mesophyll, the tissue that grows between the epidermis of the upper (upper side) and lower (underside of the leaves). It is made up of chlorenchyma, a tissue specialized in photosynthesis, and the veins of the leaves, of vascular tissue.
This type of tissue can be made up of one or two types of cells. In the first case, it is said to be homogeneous, while if it is made up of two different types of cells, it is called heterogeneous mesophyll..
In this field, the term mesophilic is used to define plants or plant formations (mesophilic forests) that inhabit moderate environmental conditions, especially in relation to moderate humidity conditions..
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