Thermophile

Classification

Thermophiles can be classified in various ways. One classification sorts these organisms according to their optimal growth temperatures:

1. Simple thermophiles: 50–64 C
2. Extreme thermophiles 65–79 C
3. Hyperthermophiles 80 C and beyond, but not below 50 C

In a related classification, thermophiles are sorted as follows:

1. Facultative thermophiles (also called moderate thermophiles) can thrive at high temperatures, but also at lower temperatures (below 50 C), whereas
2. Obligate thermophiles (also called extreme thermophiles) require such high temperatures for growth.
3. Hyperthermophiles are particularly extreme thermophiles for which the optimal temperatures are above 80 C.

60 C.]]

Many hyperthermophilic Archaea require elemental sulfur for growth. Some are anaerobes that use the sulfur instead of oxygen as an electron acceptor during anaerobic cellular respiration. Some are lithotrophs that oxidize sulphur to create sulfuric acid as an energy source, thus requiring the microorganism to be adapted to very low pH (i.e., it is an acidophile as well as thermophile). These organisms are inhabitants of hot, sulfur-rich environments usually associated with volcanism, such as hot springs, geysers, and fumaroles. In these places, especially in Yellowstone National Park, zonation of microorganisms according to their temperature optima occurs. These organisms are often colored, due to the presence of photosynthetic pigments.

Thermophile versus mesophile

Thermophiles can be discriminated from mesophiles from genomic features. For example, the GC-content levels in the coding regions of some signature genes were consistently identified as correlated with the temperature range condition when the association analysis was applied to mesophilic and thermophilic organisms regardless of their phylogeny, oxygen requirement, salinity, or habitat conditions.

Fungal thermophiles

Fungi are the only group of organisms in the Eukaryota domain that can survive at temperature ranges of 50–60 °C. Thermophilic fungi have been reported from a number of habitats, with most of them belonging to the fungal order Sordariales. Thermophilic fungi have great biotechnological potential due to their ability to produce industrial-relevant thermostable enzymes, in particular for the degradation of plant biomass.

Gene transfer and genetic exchange

Sulfolobus solfataricus and Sulfolobus acidocaldarius are hyperthermophilic Archaea. When these organisms are exposed to the DNA damaging agents UV irradiation, bleomycin or mitomycin C, species-specific cellular aggregation is induced. In S. acidocaldarius, UV-induced cellular aggregation mediates chromosomal marker exchange with high frequency. and Ajon et al.

In science

Thermus aquaticus is historically important. Its discovery pushed forward the maximum temperature in which it was believed any organism could grow, and its heat-resistant DNA polymerase enabled it to develop an efficient way to multiply DNA quickly without the enzyme being denatured, a key step in the amelioration of PCR tests.

References

References

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14. Barr, Camille. "Thermus Aquaticus". Montana Natural History Center.