Conférence "New microbes and new processes in three thermal ecosystems of Siberia, Russia"

Venez assister à ce séminaire organisé par le LM2E où notre invitée Pr Elizaveta Bonch-Osmolovskaya (Winogradsky Institute of Microbiology, Moscou) nous dévoilera des métabolismes microbiens étonnants chez de nouvelles espèces bactériennes venues de Sibérie ! Rendez-vous à 14h à l'Amphi A de l'IUEM.

RESUME

Microbial diversity was studied in three thermal ecosystems of Siberia: deep subsurface biosphere and the  hot springs of two different regions, Kamchatka and Chukotka.

We found that in the water flowing out of the abandoned oil-exploring well in Western Siberia (depth 2700 m) two populations are present: stable one consisting of thermophilic sulfate reducers and methanogens, and variable one  represented by uncultured Firmicutes, Chloroflexi and Ignavibacteria phylum nov. We assumed that the latter organisms normally are attached to buried organic matter hydrolysing polymeric substrates and enter the water as a minor and variable part of planctonic population.  Our deep subsurface isolate Melioribacter roseus gen. nov., sp. nov. makes a good example of this group, as it is able to hydrolyse numerous biopolymers and to reduce various inorganic electron acceptors.

In Kamchatka we obtained 16S rRNA profiles of 13 hot springs where an active inorganic carbon assimilation took place. Most numerous and widely distributed were the bacteria of genus Sulfurihydrogenibium (phylum Aquificeae) and uncultured archaea of family Thermoplasmataceae group A10. Unexpectedly, bacteria of genus Caldimicrobium (phylum Thermodesulfobacteria) made one of dominating groups in neutral anaerobic high-temperature hot springs. Representatives of this genus were found to be able to grow lithoautotrophically by sulfur disproportionation. It is probable that this process plays an important role in thermal environments fueling anaerobic chemolithotrophic ecosystems.

Hot springs of Chukotka are surrounded by permafrost, and so far have never been explored by microbiologists; however, their detailed geological description is available. Most common energy substrates of other terrestrial thermal environments - hydrogen sulfide and molecular hydrogen - are absent in Chukotka hot springs, but their water is rich of different metal ions. 16S rRNA profiling showed the dominance of Aquificeae, and, in some cases, of Thaumarchaeota. We assume that the microbial communities of Chukotka hot springs are performing unusual for such ecosystems energy-giving processes and the dominating microorganisms use novel for their groups inorganic electron donors.