The Dallol geothermal area, in the northern part of the Danakil Depression - at 124-155 meters below sea level - in Ethiopia, is one of the most extreme environments on earth.
Located at the triple junction between the Nubian, Somali and Arab tectonic plates, in an incipient seafloor-spreading center, the northern part of Danakil is dominated by the saline plain of Assale (an accumulation of deposits of marine evaporites), which houses the Dallol.
In Afar, Dallol can be translated as "disintegrated, or decomposed", which qualifies hot and acidic sources, with a pH close to zero, and maximum temperatures of 90 to 109 ° C, very salty, with a redox potential, and containing heavy metals.
These extreme conditions are not favorable to life, and there are only rare volcanologists, or volcanophiles, and some Afars, to stay there during very brief moments.
A team from the National Institute of Aerospace Technologies in Madrid discovered a rather special inhabitant on a chimney about a meter high. After scraping the salt, the scientists extracted a DNA corresponding with the class of nanohaloarchaea, tiny organisms surviving in hypersaline medium. It is close to Candidatus Holaredivivus sp. G17 described in hypersaline ponds of Alicante, Spain.
Using imaging techniques such as scanning electron microscopy and transmission electron microscopy, Gómez and his team recorded spherical structures around 50-500 nanometers in size. It is smaller than most archaea, according to the researchers, who concluded that they were organic based on the high carbon content of the structures.
The discovery of these microorganisms was a surprise, as Nanohaloarchaea has never been seen in acidic and high temperature environments.
" The presence of life in Dallol's hot springs broadens our understanding of the limits of habitability on Earth and beyond." The beginning of Mars was volcanically active, and some areas, such as Nili Patera Caldera, might have resembled Dallol's hot spring geology, the researchers said in their article, published in Scientific Reports in May.
Further research will be needed to understand how this nanobacteria can survive in this extreme environment and what is its role in a geochemical cycle.
Scientific reports - OPEN Article Published: 27 May 2019 - Ultra-small microorganisms in the polyextreme conditions of the Dallol volcano, northern Afar, Ethiopia - by F.Gomez & al