Extremophile

[1][2] Since the definition of an extreme environment is relative to an arbitrarily defined standard, often an anthropocentric one, these organisms can be considered ecologically dominant in the evolutionary history of the planet.

Dating back to more than 40 million years ago, extremophiles have continued to thrive in the most extreme conditions, making them one of the most abundant lifeforms.

[3] In the 1980s and 1990s, biologists found that microbial life has great flexibility for surviving in extreme environments—niches that are acidic, extraordinarily hot, or with irregular air pressure for example—that would be completely inhospitable to complex organisms.

"[6] Some bacteria were found living in the cold and dark in a lake buried a half-mile deep under the ice in Antarctica,[7] and in the Marianas Trench, the deepest place in Earth's oceans.

[8][9] Expeditions of the International Ocean Discovery Program found microorganisms in 120 °C (248 °F) sediment that is 1.2 km (0.75 mi) below seafloor in the Nankai Trough subduction zone.

[14] Tom Gheysens from Ghent University in Belgium and some of his colleagues have presented research findings that show spores from a species of Bacillus bacteria survived and were still viable after being heated to temperatures of 420 °C (788 °F).

For example, organisms living inside hot rocks deep under Earth's surface are thermophilic and piezophilic such as Thermococcus barophilus.

[26] Recent research carried out on extremophiles in Japan involved a variety of bacteria including Escherichia coli and Paracoccus denitrificans being subject to conditions of extreme gravity.

P. denitrificans was one of the bacteria which displayed not only survival but also robust cellular growth under these conditions of hyperacceleration which are usually found only in cosmic environments, such as on very massive stars or in the shock waves of supernovas.

[34][35] In September 2015, scientists from CNR-National Research Council of Italy reported that S. soflataricus survived under Martian radiation at a wavelength that was considered lethal to most bacteria.

[37] In August 2020 scientists reported that bacteria that feed on air discovered 2017 in Antarctica are likely not limited to Antarctica after discovering the two genes previously linked to their "atmospheric chemosynthesis" in soil of two other similar cold desert sites, which provides further information on this carbon sink and further strengthens the extremophile evidence that supports the potential existence of microbial life on alien planets.

[43] While most bacteria would be crushed by the pressure in these environments, piezophiles can tolerate these depths and can metabolize pollutants of concern if they possess bioremediation potential.

[citation needed] There are multiple potential destinations for hydrocarbons after an oil spill has settled and currents routinely deposit them in extreme environments.

Methane bubbles resulting from the Deepwater Horizon oil spill were found 1.1 kilometers below water surface level and at concentrations as high as 183 μmol per kilogram.

However, bacteria that are present including species of Pseudomonas, Aeromonas and Vibrio were found to be capable of bioremediation, albeit at a tenth of the speed they would perform at sea level pressure.

[citation needed] Thermophilic Thermus and Bacillus species have demonstrated higher gene expression for the alkane mono-oxygenase alkB at temperatures exceeding 60 °C (140 °F).

Fungi that have been genetically modified with cold-adapted enzymes to tolerate differing pH levels and temperatures have been shown to be effective at remediating hydrocarbon contamination in freezing conditions in the Antarctic.

[48][49] In extreme heat environments the extremophile Geobacillus thermodenitrificans has been shown to effectively manage the concentration of these metals within twelve hours of introduction.

[50] Some acidophilic microorganisms are effective at metal remediation in acidic environments due to proteins found in their periplasm, not present in any mesophilic organisms, allowing them to protect themselves from high proton concentrations.

For example, Methylacidiphilum fumariolicum, Methylorubrum extorquens, and Methylobacterium radiotolerans are known to be able to use lanthanides as cofactors to increase their methanol dehydrogenase activity.

[citation needed] Radiotrophic fungi, which use radiation as an energy source, have been found inside and around the Chernobyl Nuclear Power Plant.

In July 2019, a scientific study of Kidd Mine in Canada discovered sulfur-breathing organisms which live 7,900 feet (2,400 m) below the surface, and which breathe sulfur in order to survive.

Exposure of these organisms to the DNA damaging agents UV irradiation, bleomycin or mitomycin C induces species-specific cellular aggregation.

[citation needed] Extracellular membrane vesicles (MVs) might be involved in DNA transfer between different hyperthermophilic archaeal species.