What is the Thermophiles: The thermophiles are a subtype of extremophiles that tolerate high temperatures, between 50 °C and 75 °C, either because these temperature values are maintained in these extreme environments, or because they are frequently reached.
Thermophilic organisms are usually bacteria or archaea, however, there are metazoans (eukaryotic organisms that are heterotrophic and tissue), which also develop in warm places. (Thermophiles)
Marine organisms are also known to have adapted to these high temperatures, associated in symbiosis with thermophilic bacteria, and have developed biochemical mechanisms such as modified hemoglobin, higher blood volume, among others, that enable them to Allows to tolerate the toxicity of sulfides and compounds. Why Sulfur?
It is believed that thermophilic prokaryotes were the first simple cells in the evolution of life and inhabited places with volcanic activity and geysers in the oceans.
Examples of such thermophilic organisms are those that live near hydrothermal vents or fumaroles at the bottom of the oceans, such as methanogenic bacteria (methane producers) and annelids. Riftia pachyptilla.
Main habitats where thermophiles can be found:
- Terrestrial hydrothermal environment.
- Marine hydrothermal environment.
- hot desert.
Characteristics of thermophilic organisms
Temperature: Important abiotic factor for the growth of microorganisms
Temperature is one of the major environmental factors that affect the growth and survival of living beings. Each species has a range of temperatures between which it can survive, however, it has optimum growth and development at specific temperatures.
The growth rate of each organism can be expressed graphically versus temperature, giving values corresponding to the critical critical temperatures (minimum, optimum, and maximum).
minimum temperature
At the minimum temperature of an organism’s development, there is a decrease in the fluidity of the cellular membrane and the processes of material transport and exchange, such as the entry of nutrients and the exit of toxins, can stop.
Between the minimum temperature and the optimum temperature, the growth rate of microorganisms increases.
optimum temperature
At the optimum temperature, metabolic reactions take place with the maximum possible efficiency.
maximum temperature
Above the optimum temperature, there is a decrease in the rate of increase in the maximum temperature that can be tolerated by each organism. (Thermophiles)
At these high temperatures the structural and functional proteins are denatured and inactivated as enzymes, as they lose their geometric configuration and special spatial configuration, the cytoplasmic membrane breaks down and heat causes thermal degradation or rupture. It happens.
Each microorganism has a minimum, optimum and maximum temperature of operation and growth. Thermophiles have an exceptionally high value in all three of these temperatures.
Distinctive features of thermophilic organisms
- Thermophilic organisms have a high growth rate, but a short life span.
- Their cell membranes contain a lot of lipids or long chain saturated fats; This type of saturated fat is able to absorb heat and go into a liquid state at high temperatures (melt), without being destroyed.
- Its structural and functional proteins are very stable against heat (thermostable), through covalent bonds and special intermolecular forces known as London’s dispersion forces.
- They also have special enzymes to maintain metabolic function at high temperatures.
- It is known that these thermophilic microorganisms can use sulfides and sulfur compounds abundant in volcanic areas, as sources of nutrients to convert them into organic matter.
Classification of Thermophilic Organisms
Thermophilic organisms can be divided into three broad categories:
- Moderate thermophile, (optimal between 50-60 °C).
- Extremely thermophile (maximum close to 70 °C).
- Hyperthermophile (optimal close to 80 °C).
Thermophilic organisms and their environments
terrestrial hydrothermal environment
Hydrothermal sites are surprisingly common and widely distributed. They can be roughly divided into those that are associated with volcanic areas and those that are not.
Hydrothermal environments that present the highest temperatures are usually associated with volcanic features (boilers, faults, tectonic plate boundaries, posterior arc basins), which allow magma to rise to a depth where it mixes with groundwater. Can contact directly Shallow.
Hot spots are often accompanied by other characteristics that make life difficult, such as pH, organic matter, chemical composition and extreme salinity. (Thermophiles)
The inhabitants of terrestrial hydrothermal environments, therefore, survive in the presence of many extreme conditions. These organisms are known as polyextremophiles.
Examples of organisms that live in terrestrial hydrothermal environments
Organisms belonging to three domains (eukaryotes, bacteria and archaea) have been identified in terrestrial hydrothermal environments. The diversity of these organisms is mainly determined by temperature.
While a diverse range of bacterial species live in moderately thermophilic environments, photoautotrophs can dominate the microbial community and form macroscopic “mat” or “carpet” structures.
These “photosynthetic carpets” are present on the surface of neutral and alkaline thermal springs (pH greater than 7.0) at temperatures between 40–71 °C, with cyanobacteria established as the main major producers.
Above 55 °C, photosynthetic carpets are mainly inhabited by unicellular cyanobacteria such as Synechococcus sp.
bacteria
The photosynthetic microbial carpet may also be inhabited primarily by bacteria of the genera Chloroflexus and Roseiflexus , both members of the order Chloroflexus.
When they are associated with cyanobacteria, species of Chloreflexus and Roseiflexus grow better in photoheterotrophic conditions.
If the pH is acid, then the common genera are Acidiosfera, Acidiphilium, Desulfotomaculum, Hydrogenobaculum, Methylocorus, Sulfobacillus thermoanaerobacterium, Thermodesulfobium and Thermodesulfator.
In hyperthermophilic sources (between 72–98 °C) it is known that photosynthesis does not occur, which allows the predominance of chemolithoautotrophic bacteria.
These organisms belong to the phylum Aquiphae and are cosmopolitan; Can oxidize hydrogen or molecular sulfur with oxygen as an electron acceptor and fix carbon via the reducing tricarboxylic acid (rTCA) pathway.
archaea
The majority of cultivated and non-cultivated archaic craniarportal fumes have been identified in neutral and alkaline thermal environments.
Species such as Thermophilum pendens, Thermosphaera aggregans or Stetteria hydrophila Nitrosocaldus yellowston , propagation below 77 °C Thermoproteus neutrophilus, Vulcanisata dista, Thermophilum pendens , Aeropyruni perinix, Desulfucrocus mobilis and Ignisphaera agrins in sources with temperatures above 80 °C.
In acidic environments, the types of genera are: Sulfolobus, Sulfuroccus, Metallosphaera, Acidianus, Sulfurifera, Pyrophilus, Thermoplasma and Galdivirga.
eukaryotic
Neutral and alkaline sources can be cited within eukaryotes as Thermomys lanuginos, Scythelidium thermophilum, Echinomeba thermarum, Marinomeba thermophilia and Oramoeba funiorolia.
Among the acid sources you can find the styles: Pinnularia, Cynidioszone, Cyanidium or Galdieria .
marine hydrothermal environment
With temperatures ranging from 2 °C to over 400 °C, pressures in excess of several thousand pounds per square inch (psi), and high concentrations of toxic hydrogen sulfide (pH 2.8), deep-sea hydrothermal vents occur. Possibly the most extreme atmosphere on our planet.
In this ecosystem, microbes act as lower links in the food chain, deriving their energy from geological heat and chemicals that are found deep in the Earth’s interior.
Examples of organisms associated with marine hydrothermal environments
The organisms associated with these sources or vents are very diverse, and the existing relationships between the various taxa are not yet fully understood.
The species that have been isolated are both bacteria and archaea. For example, archaea of the genus Methanococcus, Methanopus and anaerobic thermophilic bacteria of the genus Caminibacter have been isolated .
Bacteria grow in biofilms that feed on many organisms such as amphipods, copepods, snails, lobster crabs, tubular worms, fish and octopuses.
A common panorama consists of accumulations of mussels, Bathiomodyles thermophilus , over 10 cm in length, which burrow into crevices of basaltic lava. These commonly occur with many Galapagos crabs ( Munidopsis subquamosa ).
One of the most unusual organisms found is the tubular worm Riftia pachyptilla , which can be classified as large and can reach a size of close to 2 meters.
These tubular worms have no mouth, stomach, or anus (ie, they do not have a digestive system); They are completely closed bags, without any external environment.
The bright red color of the pen at the tip is due to the presence of extracellular hemoglobin. Hydrogen sulfide is transported through the cell membrane attached to the filaments of this pen, and through extracellular hemoglobin it reaches a specialized “tissue” called the trophosome, which is composed entirely of symbiotic chemosynthetic bacteria. ..
It can be said that these worms have an internal “garden” of bacteria that feed on hydrogen sulfide and provide “food” for the worm, an extraordinary adaptation.
hot desert
Hot deserts cover between 14 and 20% of the Earth’s surface, about 19–25 million km.
The hottest deserts, such as the Sahara of North Africa and the deserts southwest of the Americas, Mexico and Australia, are found in both the tropics of the Northern Hemisphere and the Southern Hemisphere (between about 10° and 30°). 40 ° latitude).
type of desert
A defining characteristic of a hot desert. According to the Köppen-Geiger climate classification, deserts are regions with an annual rainfall of less than 250 mm.
However, annual rainfall can be a misleading index, as water loss is a deciding factor in the water budget.
Thus, the United Nations Environment Program’s definition of desert is the annual loss of humidity under normal climatic conditions, where the potential evapotranspiration (PET) is five times greater than the actual precipitation (P).
High PET predominates in hot deserts, because due to the lack of cloud cover, solar radiation tends to be maximum in arid regions.
Deserts can be divided into two types according to their level:
- Hyperáridos: with an index of acidity (P / PET) less than 0.05.
- Aggregates: with an index between 0.05 and 0.2.
Deserts differ from arid-arid lands (P / PET 0.2–0.5) and arid sub-humid arid lands (0.5–0–65).
Deserts have other important characteristics, such as their strong temperature changes and the high salinity of their soils.
On the other hand, a desert is usually associated with dunes and sand, however, this image only corresponds to 15-20% of them all; Rocky and mountainous landscapes are the most desert environments.
Examples of thermophilic organisms of the desert
The inhabitants of the desert, who are thermophiles, have a series of adaptations to face adversities, which arise from the lack of rain, high temperatures, winds, salinity, among others.
Xerophyte plants have evolved strategies to avoid transpiration and store as much water as possible. Thickening of stems and leaves and leaves is one of the most commonly used strategies.
This is evident in the Cactaceae family, where the leaves have also been modified into spines, both to avoid evaporation and to repel herbicides.
Ling Lithops or stone plants, which are native to the Namibian desert, also develop succulents, but in this case the plant grows at ground level, camouflaging itself with surrounding stones.
On the other hand, animals living in these extreme habitats develop all kinds of adaptations, from physical to moral. For example, the so-called kangaroo rats have a low volume, a small amount of urine, and these animals are very efficient in their water-scarce environment.
Another mechanism for reducing water loss is an increase in body temperature; For example, the body temperature of camels can rise from about 34 °C to 40 °C in summer.
Temperature variation is of great importance in water conservation for the following reasons:
- An increase in body temperature means that heat is stored in the body rather than dissipated through evaporation of water. Later, at night, the excess heat can be expelled without water.
- The temperature of a hot environment decreases, as the temperature gradient decreases.
Another example is the sand rat ( Psammomys obesus ), which have evolved a digestive system that allows them to feed only on desert plants of the family Chenopodiaceae, the leaves of which contain large amounts of salts.
The moral (behavioral) adaptations of desert animals are many, but perhaps the most obvious one implies that the activity-rest cycle is reversed.
In this way, these animals become active at sunset (nocturnal activity) and cease to live at dawn (day rest), their active life does not coincide with the warmer hours.
