Thermoactinomyces spp.: Thermophilic Bacteria from geothermal springs in Armenia.

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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Extremophilic Micro-organismss from the Dallol Geothermal Springs of the Danakil Depression in northern Ethiopia.

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 Danakil Depression of northern Ethiopia is extremely volcanically active, with dozens of volcanoes fed by an emerging divergent margin along the East African Rift; Erta Ale is on the Ethiopian Rift, the boundary between the Nubian Plate and the Danakil Microplate. This creates a series of volcanic systems within what is one of the hottest and driest deserts on Earth. The Dallol Geothermal Springs of the Danakil Depression are thought to have formed in 1926 following a phraetic eruption (explosion caused by water coming into contact with hot magma). The water that reaches the surface here is typically at boiling point (~100°C), highly acidic (pH ~0), and saturated with salts and heavy metals and salts, creating a series of pools of varying colours, which reflect their metal contents. The system has been proposed as a possible Earthly analogue of the Nili Patera Caldera on Mars, which is interpreted as an ancient hydrothermal volcanic system.

In a paper published in the journal Scientific Reports on 27 May 2019, Felipe Gómez of the Centro de Astrobiología, Barbara Cavalazzi of the Dipartimento di Scienze Biologiche, Geologiche e Ambientali at the Università di Bologna, and the Department of Geology at the University of Johannesburg, Nuria Rodríguez, also of the Centro de Astrobiología, Ricardo Amils, again of the Centro de Astrobiología, and of the Centro de Biología Molecular “Severo Ochoa” Cantoblanco, Gian Gabriele Ori of the International Research School of Planetary Sciences at the Universitá d’Annunzio, and the Ibn Battuta Centre at the Université Cadi Ayyad, Karen Olsson-Francis of the School of Environment, Earth and Ecosystems Sciences at the Open University, Cristina Escudero and Jose Martínez, also of the Centro de Biología Molecular “Severo Ochoa” Cantoblanco, and Hagos Miruts of the Department of Earth Sciences at Mekelle University, describe the presence of Extremophilic Micro-organismss from the Dallol Geothermal Springs.

The site contained numerous 'chimneys', formed where superheated water reaches the surface and precipitates out its mineral content. Gómez et al. extracted samples from one of these chimneys, as well as the pool surrounding it. The water within the chimney was found to be pH 0.25 and 86 °C, while that in the pool was pH 2.42 and 47 °C.

Panoramic view of the sampling sites (D9: central small chimney and D10: water from the blue pool at the bottom of the chimney). Gómez et al. (2019).

DNA was successfully extracted from the salt precipitates at the chimney; this was found to have come from an unknown Nanohaloarchaean (member of a group of very small, extemophilic Archaeans), which appears to be related to an as-yet-unnamed strain from a salt pond in Alicante, referred to as Candidatus Holaredivivus sp. G17. Scanning electron microscopy of salt crystals from the chimney revealed the presence of small micro-organisms entombed within precipitated silica minerals, which may suggest that the micro-organisms play a role in the mineralisation process.Hot Sp

(A) General view of the sampling site, (B) the small chimneys (temperature of water 90 °C. (C) D9 sample from a small chimney in (A). (D–L) SEM and (M–O) Scanning TEM images of sample D9 showing the morphologies of ultra-small microorganisms entombed in the mineral layers. Gómez et al. (2019).

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Tourist dies after falling into hot spring at Yellowsone National Park.

A man has died after falling into a hot spring at Yellowstone National Park in Wyoming, USA. The incident happened in June this year, but details of the event have only become clear following a Freedom of Information Act request by a local radio station. Colin Scott, 23, of Oregon was reportedly visiting the park with his sister on 7 June when he left a designated boardwalk in the Norris Geyser Basin in order to investigate the temperature of a pool, apparently with the intention of  'hot-potting' (getting into the pool and soaking), a practise strictly forbidden in the park. However he slipped and fell into the pool, possibly after being scalded by the water, and was rapidly killed by the hot and acidic water. Attempts to recover his body that day were unsuccessful, in part due to a large thunderstorm in the area, and by the next day little was left of the body.

Boardwalk across the Norris Geyser Basin in the Yellowstone National Park. InSapphoWeTrust/Wikimedia Commons.

The Yellowstone National Park lies on top of the caldera of an active volcano. The hot springs are fuelled by water from the surface peculating through the ground until it encounters hot rocks or magma, which heats it rapidly. This hot water then rises back to the surface to fuel the geysers and fill the volcanic pools of the park. As it passes through the rocks the water absorbs chemicals from the surrounding minerals, with water with different mineral properties in different parts of the park, creating a variety of brightly coloured pools. 

  Yellowstone is home to one of the world’s largest active volcanic systems. Cataclysmic eruptions in the past few million years created huge volcanic depressions called “calderas.” The youngest, the Yellowstone Caldera, was formed 640 000 years ago. Since then, about 80 eruptions of rhyolite (thick, sticky lava) and basalt (more-fluid lava) have occurred. The caldera’s interior is largely covered by rhyolites, most erupted in the past 160 000 years. Large hydrothermal (steam)-explosion craters formed in the past 14 000 years are located near Yellowstone Lake and in major geyser basins. Recent earthquakes (1973 to 2002) were concentrated between Hebgen Lake and the Norris Geyser Basin and along faults. USGS.

Many of these pools are alkaline in nature, but the pools of  the Norris Geyser Basin are acid, with a typical pH of about 3.5. This is not immediately dangerous, being roughly as acidic as vinegar, Lemon juice or some fizzy drinks. However the water in the pool was about 100°C (i.e. boiling), hot enough to quickly kill anyone falling in. Once immersed in such a pool the acid would rapidly attack the body, as, like most chemical reactions, acids act more strongly at higher temperatures.

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Cooking the primordial soup; did the first life emerge in volcanic pools?

The blood plasma and lymph of modern animals is similar in chemical composition to seawater, strongly supporting the idea that animal life began in the oceans, but the liquid inside our cells has a quite different chemistry, suggesting that cells themselves first arose in a different environment, since the first cells are unlikely to have shared modern cells ability to maintain an interior chemistry very different to the liquid outside their membranes.

In a paper published online in the Proceedings of the National Academy of Sciences on 13 February 2012, a team of scientists led by Armen Mulkidjanian of the School of Physics at University of Osnabrück and the A. N. Belozersky Institute of Physico-Chemical Biology at Moscow State University, describe a review of our understanding of the chemistry of the earliest cells and the environment on the early Earth in these cells are thought to have inhabited, and the conclusions drawn from this.

The oldest known rocks on Earth are about 4 billion years old, but life is thought to have originated earlier than this (life does not pre-date rocks, just any rocks still around), in a period known at the Hadean. This makes the chances of finding direct evidence of the earliest life effectively nil, but does not stop us speculating, as we are still able to make inferences about the environment on the Hadean Earth.

An artist's impression of the Hadean Earth. The continents were still assembling from thousands of volcanic island arcs, the moon was closer, the sun dimmer, the planet was being constantly bombarded by meteors, the atmosphere rich in Carbon Dioxide but entirely lacking in Oxygen, consequently there was no Ozone layer and the planet was constantly bathed in ultra-violet radiation. From the Palaeos website.

The oldest, conserved, proteins found in all organisms tend to use Zinc and Manganese, but not Iron, which is used by more modern proteins that have evolved separately in different groups, implying that the first cells evolved in an environment rich in Zinc and Manganese, but poor in Iron. Water from hydrothermal vents tends to be rich in Zinc, Manganese and Iron, but the iron precipitates out of solution rapidly.

All known cells maintain an interior environment richer in Potassium than in Sodium; the reverse of the situation found in the modern ocean. We do not have any evidence that suggests the situation in the earliest oceans would have been any different. Hydrothermal vents in the seas have similar Sodium/Potassium ratios to seawater, since this is where the water in them derives from, and the contribution of Sodium and Potasium ions from the seawater outweighs the volcanic contribution. Terrestrial hydrothermal springs derive their water from precipitation (rain and snow), which lacks Sodium and Potassium ions. The Sodium/Potassium ratio in such pools is variable; those which are dominated by water that is emitted in a liquid tend to be rich in Sodium, but those where water is emitted as a gas and then condenses tend to be rich in potassium.

All cells maintain a high interior Phosphate concentration, but the oceans are not rich in Phosphates, and there is no reason to believe the early oceans were any different. Water from volcanic vents tends to be rich in Phosphates.

Previous theories have suggested that life may have originated around deep-sea hydrothermal vents, but these have steep chemical gradients, and chemistry unlike that found inside cells. Hydrothermal pools on-land tend to have stable chemistry, but are very acidic, and so have been discounted as a likely source of life by many studies. However this acidity is caused by the reaction of Sulphur-compounds with Oxygen in the atmosphere, something that could not have happened in an ancient environment lacking atmospheric Oxygen.

The other objection to terrestrial hydrothermal pools as a place of origin for life is the high level of ultra-violet radiation that would have bathed the early Earth and which is harmful to life. The modern world is protected from ultra violet radiation by the Ozone Layer, but Ozone (O₃) is a form of Oxygen, so this would not have existed prior to the evolution of an Oxygen rich atmosphere. Water also protects against ultra-violet radiation, but there needs to be enough of it; the sea would protect early cells, but shallow pools would probably not. However Sulphur from volcanic vents, if it was not reacting with oxygen from the atmosphere, would probably react with Manganese and Zinc if they were present in the same pools of water. Sulphur compounds of Manganese and Zinc are good at absorbing ultra violet radiation, offering protection to any life living in these pools.

See also A deep-sea hydrothermal vent community discovered in the Mariana Trench, The oldest animals - Pre-Ediacaran Sponges from Namibia(?) and Did the first land plants cause an Ordovician glaciation?