Cultivation of a novel cold-adapted nitrite oxidizing betaproteobacterium from the Siberian Arctic

Permafrost-affected soils of the Siberian Arctic were investigated with regard to identification of nitrite oxidizing bacteria active at low temperature. Analysis of the fatty acid profiles of enrichment cultures grown at 4°C, 10°C and 17°C revealed a pattern that was different from that of known nitrite oxidizers but was similar to fatty acid profiles of Betaproteobacteria. Electron microscopy of two enrichment cultures grown at 10°C showed prevalent cells with a conspicuous ultrastructure. Sequence analysis of the 16S rRNA genes allocated the organisms to a so far uncultivated cluster of the Betaproteobacteria, with Gallionella ferruginea as next related taxonomically described organism. The results demonstrate that a novel genus of chemolithoautotrophic nitrite oxidizing bacteria is present in polygonal tundra soils and can be enriched at low temperatures up to 17°C. Cloned sequences with high sequence similarities were previously reported from mesophilic habitats like activated sludge and therefore an involvement of this taxon in nitrite oxidation in nonarctic habitats is suggested. The presented culture will provide an opportunity to correlate nitrification with nonidentified environmental clones in moderate habitats and give insights into mechanisms of cold adaptation. We propose provisional classification of the novel nitrite oxidizing bacterium as 'Candidatus Nitrotoga arctica'

Survival of Methanogenic Archaea from Siberian Permafrost under Simulated Martian Thermal Conditions

Since ESA mission Mars Express determined water on Mars, a fundamental requirement for life, as well as the presence of CH4 in the Martian atmosphere, which could only have originated from active volcanism or from biological sources, it is obviously that microbial life could still exist on Mars, for example in the form of subsurface lithoautotrophic ecosystems, which are also exist in permafrost regions on Earth. Present work deals with the resistance investigation of methanogenic archaea from Siberian permafrost complementary to the already well-studied methanogens from non-permafrost habitats under simulated Martian conditions. The methanogenic archaea in pure cultures as well as in permafrost samples represent higher survival potential (up to 90 percent) than the referent organisms (0.3-5.8 percent) after 22 days of exposure to thermo-physical Martian conditions at low- and mid-latitudes. It is suggested that methanogens from terrestrial permafrost seem to be more resistant against Martian conditions and could be used as a prime candidates for the search for extraterrestrial life