Extremophilic organisms live, and often thrive, in environments that
would be immediately lethal to most other life, such as boiling hot
springs, hyperardid deserts, in strong acids, or in the presence of high
levels of heavy metals or salts. The study of such organisms helps
scientists to understand the limits at which life can exist, and can
potentially give us insights into the potential for life on other
planets. The genus Thermoactinomyces currently contains five species of thermophilic Firmicute Bacteria, related to the food-poisoning Bacterium Listeria and the pathogenic Staphylococcus and Bacillus.
In a paper published in the journal Environmental Sustainability on 11 June 2019, Hovik Panosyan of the Department of Biochemistry, Microbiology and Biotechnology at Yerevan State University describes members of genus Thermoactinomyces from two geothermal springs in Armenia.
The Akhurik spring is situated in Shirak Province in northern Armenia, at an altitude of 1430 m above sealevel. Water here emerges from the outlet at 30°C, with a pH of 6.5 and a high mineral content. The Tatev Spring is situated in Syunik Province in southern Armenia. Water here emerges at 27.5°C, with a pH of 7.5 and agsain with a high mineral content.
Map of Armenia showing locations of Akhurik (1) and Tatev (2). Panosyan (2019).
A strain of Thermoactinomyces was isolated from the Akhurik Hot Spring, given the designation Isolate AkhA-12. This strain was able to grow at 37-60°C with optimum growth at about 50°C, and at pH ranges of 5.0-8.0, again with optimum growth at pHs of 7.0-7.2; the species was also able to lolerate salt at concentrations of up to 8%. Panosyan notes that the Bacteria were found living in waters cooler than the minimum temperature at which it was possible to cultivat them in the lab, but also that the water feeding the spring is known to reach 99°C a little way beneath the surface.
Akhurik hot spring (vigorous degassing and cyanobacterial mats are visible). Panosyan (2019).
The Tatev Hot Spring also yielded a strain of Thermoactinomyces, which was identified as Isolate Tatev 35a. This strain was able to grow at 35-60°C with optimum growth at 50-55°C, and at pH ranges of 5.0-8.0, again with optimum growth at pHs of
7.2-7.4. This strain could coope with salt concentrations of up to 5%, and (unlike AkhA-12) appeared to be capable of reducing nitrates (most organisms respire using oxygen, a process in which the oxygen is
'reduced' by when it accepts an electron from a donor atom, typically
carbon - electrons have a negative charge, so the charge on the oxygen
atom goes down when it accepts an electron, hence it is reduced, even
though it has gained something).
Tatev hot spring. Panosyan (2019).
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