Extremophiles… unexpected worlds
Researches about extremophilic microorganisms, species which thrives in extreme conditions that are detrimental to the majority of life on Earth, constitute many promising “worlds to discover”. In terms of biodiversity, those unexpected forms of life show that the inventory of all species living on Earth is far from being done. Extremophilic microorganisms also reveal their amazing adaptive strategies, which reinforces the possibility of life on other planets.The particularities of Pyrococcus CH1
The piezophilic microorganisms constitute a subgroup of extremophiles. Discovered on the site “Ashadze ”(2) at 4100 m depth, CH1 strain was successfully isolated and assigned to the genus Pyrococcus, within the Euryarchaeota lineage of the Archae domain. This organism grows within a temperature range of 85 to 105°C and a pressure range of 15 to 150 MPa, with optima for 98°C and 52 MPa respectively. It is unable to grow for pressures below 15 MPa.
Pyrococcus CH1 is the first obligate piezo-hyperthermophilic(3) archaeon from the deepest vent field explored so far.
This discovery extends the physical and chemical limits of life on Earth and strengthens the idea of the existence of a hyperthermophilic biosphere in the depth of our planet. The study of the microorganisms in the seabed sediments of ocean plates seems very promising. Indeed, the hydrothermal vents offer extremes conditions of temperature, pressure and fluids composition for the microorganisms. What are the possible benefits of those microorganisms?
Thanks to extreme conditions of developpement, their enzymes are thermostable and able to function in reactors under pressure. It is tempting to use them in industrial processes, which require high levels of temperature and pressure, notably to gain high value added products, presently resulting from fine chemistry.
1) The Serpentine cruise was lead by Yves Fouquet, Head of GEODE Multi-disciplinary Studies of Extreme Environments in the Deep Seas and head of the Geochemistry and Metallogeny Laboratory of Ifremer Brest. It has gathered geologists, geochemists, biologists and microbiologists.
2) At 4100 m depth, « Achadze » is the deepest active hydrothermal site known so far. It was explored for the first time with the ROV Victor 6000 operated from Ifremer's research vessel Pourquoi pas?.
3) A piezophile (also called a barophile) is an organism which thrives at high pressures, a hyperthermophile, an organism which thrives in extremely hot environments.