Global ecological patterns in uncultured archaea

9 páginas, 5 figuras.We have applied a global analytical approach to uncultured Archaea that for the first time reveals well-defined community patterns along broad environmental gradients and habitat types. Phylogenetic patterns and the environmental factors governing the creation and maintenance of these patterns were analyzed for c. 2000 archaeal 16S rRNA gene sequences from 67 globally distributed studies. The sequences were dereplicated at 97% identity, grouped into seven habitat types, and analyzed with both Unifrac (to explore shared phylogenetic history) and multivariate regression tree (that considers the relative abundance of the lineages or taxa) approaches. Both phylogenetic and taxon-based approaches showed salinity and not temperature as one of the principal driving forces at the global scale. Hydrothermal vents and planktonic freshwater habitats emerged as the largest reservoirs of archaeal diversity and consequently are promising environments for the discovery of new archaeal lineages. Conversely, soils were more phylogenetically clustered and archaeal diversity was the result of a high number of closely related phylotypes rather than different lineages. Applying the ecological concept of ‘indicator species’, we detected up to 13 indicator archaeal lineages for the seven habitats prospected. Some of these lineages (that is, hypersaline MSBL1, marine sediment FCG1 and freshwater plSA1), for which ecological importance has remained unseen to date, deserve further attention as they represent potential key archaeal groups in terms of distribution and ecological processes. Hydrothermal vents held the highest number of indicator lineages, suggesting it would be the earliest habitat colonized by Archaea. Overall, our approach provided ecological support for the often arbitrary nomenclature within uncultured Archaea, as well as phylogeographical clues on key ecological and evolutionary aspects of archaeal biology.This research was supported by grant CRENYC CGL2006- 12058 to EOC from the Spanish Ministerio de Educacio´n y Ciencia (MEC), and CONSOLIDER-INGENIO 2010 project GRACCIE CSD2007-00004. JCA benefits from a Juan de la Cierva-MEC postdoctoral fellow, and AB is supported by an FPU-MEC predoctoral scholarship.Peer reviewe

Co-occurence of Crenarchaeota, Thermoplasmata and methanogens in anaerobic sludge digesters

International audience16S rRNA Crenarchaeota and Thermoplasmata sequences retrieved from 22 anaerobic digesters were analysed. 4.8 and 0.53 % of archaeal sequences were simultaneously affiliated to these lineages. A core of 2 operational taxonomic units (OTUs) representing 0.6 to –33.6 % of all archaeal sequences were defined for the Crenarchaeotes and identified to already known but not yet cultivable organisms in almost half of the digesters sampled. For the Thermoplasmata, apparently less abundant with 0.7 to –4.7 % of the archaeal sequences, 3 OTUs were identified. We showed here that Crenarchaeotes coexist with methanogens and are particularly abundant when Arch I lineage (also called WSA2 by Hugenholtz) is dominant in digesters. Moreover, Thermoplasmata were detected when Crenarchaeota were present. Interactions between methanogens, Crenarchaeotea and Thermoplamata were thus discussed

Temporal evolution of methane cycling and phylogenetic diversity of archaea in sediments from a deep-sea whale-fall in Monterey Canyon, California

Whale-falls represent localized areas of extreme organic enrichment in an otherwise oligotrophic deep-sea environment. Anaerobic remineralization within these habitats is typically portrayed as sulfidogenic; however, we demonstrate that these systems are also favorable for diverse methane-producing archaeal assemblages, representing up to 40% of total cell counts. Chemical analyses revealed elevated methane and depleted sulfate concentrations in sediments under the whale-fall, as compared to surrounding sediments. Carbon was enriched (up to 3.5%) in whale-fall sediments, as well as the surrounding sea floor to at least 10 m, forming a 'bulls eye' of elevated carbon. The diversity of sedimentary archaea associated with the 2893 m whale-fall in Monterey Canyon (California) varied both spatially and temporally. 16S rRNA diversity, determined by both sequencing and terminal restriction fragment length polymorphism analysis, as well as quantitative PCR of the methyl-coenzyme M reductase gene, revealed that methanogens, including members of the Methanomicrobiales and Methanosarcinales, were the dominant archaea (up to 98%) in sediments immediately beneath the whale-fall. Temporal changes in this archaeal community included the early establishment of methylotrophic methanogens followed by development of methanogens thought to be hydrogenotrophic, as well as members related to the newly described methanotrophic lineage, ANME-3. In comparison, archaeal assemblages in 'reference' sediments collected 10 m from the whale-fall primarily consisted of Crenarchaeota affiliated with marine group I and marine benthic group B. Overall, these results indicate that whale-falls can favor the establishment of metabolically and phylogenetically diverse methanogen assemblages, resulting in an active near-seafloor methane cycle in the deep sea