The thermophilic bacteria They are those that have the capacity to develop in environments with temperatures greater than 50 ° C. The habitats of these microorganisms are very hostile places, such as hydrothermal vents, volcanic areas, hot springs and deserts, among others. Depending on the temperature range they support, these microorganisms are classified as thermophiles, extreme thermophiles, and hyperthermophiles..
Thermophiles develop in a temperature range between 50 and 68 ° C, with their optimum growth temperature being more than 60 ° C. Extreme thermophiles grow in a range of 35 to 70 ° C, with an optimal temperature of 65 ° C, and hyperthermophiles live in a temperature range of 60 to 115 ° C, with optimal growth at ≥80 ° C..
Examples of thermophilic bacteria in general include the following: Geobacillus stearotermophilus, Deferribacter desulfuricans, Marinithermus hydrothermalis, Y Thermus aquaticus, among others.
These microorganisms have special structural characteristics that provide them with the ability to withstand high temperatures. In fact, their morphology is so different that they cannot develop at lower temperatures..
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Thermophilic bacteria have a series of characteristics that make them adapted to environments with very high temperatures..
On the one hand, the cell membrane of these bacteria has a high amount of long-chain saturated lipids. This allows them to withstand high temperatures and maintain adequate permeability and flexibility, managing to exchange substances with the environment without destroying themselves..
On the other hand, although it is known that proteins generally denature at high temperatures, the proteins present in thermophilic bacteria possess covalent bonds that interact hydrophobically. This characteristic provides stability to this type of bacteria..
Likewise, the enzymes produced by thermophilic bacteria are thermostable proteins, since they can perform their functions in the hostile environments where these bacteria develop, without losing their configuration..
In relation to their growth curve, thermophilic bacteria have a high reproduction rate, but have a shorter half-life than other classes of microorganisms.
Today, different types of industries use enzymes of bacterial origin to carry out different processes. Some of them come from thermophilic bacteria.
Among the enzymes most frequently isolated from thermophilic bacteria with possible industrial applications are the enzymes α-amylases, xylanases, DNA polymerase, catalases, and serine proteases, all thermostable..
These enzymes are special because they are capable of acting at high temperatures, where other similar enzymes made by mesophilic bacteria would be denatured..
Therefore, they are ideal for processes that require high temperatures or in processes where it is essential to minimize the proliferation of mesophilic bacteria..
As an example of the use of enzymes from thermophilic bacteria in industry, we can mention the use of DNA polymerase (taq polymerase), in the polymerase chain reaction (PCR) technique..
This technique denatures DNA at high temperatures, without the risk of damaging the taq polymerase enzyme. The first taq polymerase used was isolated from the species Thermus aquaticus.
On the other hand, thermophilic bacteria can be used to minimize the damage caused by environmental pollution..
For example, research has revealed that some thermophilic bacteria can eliminate compounds that are toxic to the environment. Such is the case of polychlorobiphenyl (a polluting substance present in plastics and refrigerants, among other compounds).
This is possible thanks to the fact that certain thermophilic bacteria can use elements such as biphenyl, 4-chlorobiphenyl and benzoic acid as a carbon source. Therefore, they degrade polychlorinated biphenyls, eliminating them from the environment..
On the other hand, these bacteria are excellent at recycling elements such as nitrogen and sulfur in the soil. Due to this, they can be used to naturally fertilize the land without the need for artificial (chemical) fertilizers..
Likewise, some researchers propose the use of thermophilic bacteria to obtain substances that generate alternative energy such as biogas, biodiesel and bioethanol through the hydrolysis of agro-industrial waste, favoring bioremediation processes..
The habitat of thermophilic bacteria is made up of terrestrial or marine places characterized by their high temperatures. Other factors that accompany the temperature are the pH of the medium, the concentration of salts and the chemical compounds (organic and inorganic) that may be present..
Depending on the specific characteristics of the medium, a certain type of thermophilic bacteria or another will develop in it..
Among the most common habitats for this type of bacteria, the following can be mentioned: hydrothermal vents, volcanic areas, hot springs, and deserts..
Thermophilic bacteria generally require complex culture media to grow. Among the nutrients they may require are the following: yeast extract, tryptone, casamino acids, glutamate, proline, serine, cellobiose, trehalose, sucrose, acetate, and pyruvate.
An agar used for the isolation of some thermophilic bacteria is Luria-Ber-tani agar. Contains casein hydrolyzate, yeast extract, NaCl, agar, and distilled water with pH adjusted to 7.0 ± 0.2.
Most thermophilic bacteria are saprophytic and do not cause disease in humans. However, in the manufacture of food there may be factors that favor the proliferation of thermophilic microorganisms, which can be harmful..
To give an example, in the manufacture of dairy products, pasteurization is used as a method of decontamination of food. This method is supposed to guarantee sanitary quality; however, it is not foolproof as sporulated thermophilic bacteria can survive this process..
This is because, although the vegetative cell of most sporulated bacteria is not heat resistant, the spores are..
There are sporulated bacteria that represent a real danger for human consumption. For example, the spores of the following species: Bacillus cereus, Clostridium botulinum, Clostridium perfringens, Thermoanaerobacterium xylanolyticum, Geobacillus stearothermophilus.
Low acid canned goods are normally attacked by spore-forming anaerobic thermophilic bacteria such as Geobacillus stearothermophilus. This bacteria ferments carbohydrates and produces an unpleasant sour taste due to the production of short chain fatty acids..
Likewise, canned foods with high acidity can become contaminated with Clostridium thermosaccharolyticum. This microorganism is highly saccharolytic and causes bulging of the can due to high gas production.
For his part, Desulfotomaculum nigrificans it also attacks canned foods. Although the can does not show any signs of tampering, when uncapping the can you can smell a strong acidic smell and a blackened food is observed. The black color is due to the fact that the bacteria produce hydrogen sulfide, which in turn reacts with the iron in the container, forming a compound of this color..
Finally, Bacillus cereus and Clostridium perfringens produce food poisoning and Clostridium botulinum secretes a powerful neurotoxin in food that causes death when consumed.
Marine bacteria, Gram negative, heterotrophic, aerobic and hyperthermophilic bacillus.
Anaerobic bacteria, Gram positive, extreme thermophilic, sporulated.
They are aerobic hyperthermophilic bacteria, heterotrophic, with variable Gram.
Gram negative, aerobic, extreme thermophilic and halophilic bacillus. Its production of thermostable enzymes has been studied, especially to hydrolyze polysaccharides and for DNA synthesis, both of interest to the industry..
Anaerobic bacteria, extreme thermophilic, heterotrophic, reducing sulfur, nitrate and arsenate.
Gram negative rods or filaments, extreme thermophilic, strict aerobic heterotrophic.
Marine species, hyperthermophilic, anaerobic, Gram negative, chemolytoautotrophic (sulfate reducing), non-sporulated.
Gram negative, hyperthermophilic, heterotrophic and aerobic bacteria. Synthesizes a thermostable enzyme used in the PCR technique called taq DNA polymerase.
Extreme thermophilic, microaerophilic chemolytoautotrophic, thiosulfate oxidant.
Gram positive rods, sporulated, extreme thermophilic. Its spores are used in microbiology laboratories as a biological control to evaluate the proper functioning of the autoclave..
The species of this genus are characterized by being Gram negative, hyperthermophilic, although their growth range is wide, of marine life, they do not form spores, they are obligate anaerobes or microaerophiles..
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