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 41C, 101C and 171C 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 101C 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 171C. 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'.

Activated sludge from the municipal waste water treatment plant in Hamburg was seeded with mineral nitrite medium and incubated at 10°C, 17°C and 28°C. Dominant lithoautotrophic nitrite-oxidizing bacteria have been identified by electron microscopy, denaturing and temperature gradient gel electrophoresis and PCR with genus-specific primer pairs. The results have revealed the existence of three different genera of nitrite-oxidizing bacteria, namely Nitrospira, Nitrobacter and a novel cold-adapted nitrite oxidizer. As shown by electron microscopy members of the novel genus coexisted in activated sludge together with Nitrospira. A temperature-dependent shift in the population structure was demonstrated by cultivation-based approaches. The novel nitrite oxidizer was enriched at temperatures of 10°C and 17°C. Representatives of Nitrospira were able to grow in a broad temperature range between 10°C and 28°C and members of Nitrobacter were enriched during incubations at 17°C and 28°C. By subsequent 16S rDNA sequencing, the cold-adapted nitrite oxidizer was shown to be closely related to the betaproteobacterium 'Candidatus Nitrotoga arctica'. These findings demonstrated that the population structure of nitrite-oxidizing bacteria in activated sludge is more complex than previously thought and responds strongly to long-term temperature changes.

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This study reveals the first analyses of the composition and activity of the microbial community of a saline CO 2 storage aquifer. Microbial monitoring during CO 2 injection has been reported. By using Fluorescence in situ Hybridisation (FISH), we have shown that the microbial community was strongly influenced by the CO 2 injection. Before CO 2 arrival, up to 6x10 6 cells ml -1 were detected by DAPI-staining at a depth of 647 m below the surface. The microbial community was dominated by the domain Bacteria that represented approximately 60 to 90 % of the total cell number, with Proteobacteria and Firmicutes as the most abundant phyla comprising up to 47 % and 45 % of the entire population, respectively. Both the total cell counts as well as the counts of the specific physiological groups revealed quantitative and qualitative changes after CO 2 arrival. Our study revealed temporal shifts in the microbial community from chemoorganotrophic to chemolithotrophic populations, as evidenced by the outcompetition of sulphate-reducing bacteria by methanogenic archaea. In addition, an enhanced activity of the microbial population after five months CO 2 storage indicated that the bacterial community was able to adapt to the extreme conditions of the deep biosphere and to the extreme changes of these atypical conditions.

BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports—among others—the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit.