Using metagenome based genome reconstruction to understand bacterial and archaeal assemblages in the Southern Ocean

Abstract

Microbial communities (bacteria and archaea. are ubiquitous in nature and have been identified as key regulators of biogeochemical cycles. Due, in part, to challenges in cultivation of 99% of microorganisms, little is known regarding the precise mechanisms which allow microbial guilds to perform their ecological roles. To bypass such ‘cultivation bottle-neck’, alternative culture independent approaches are used to generate immense datasets, which offer crucial insights into microbial metabolic potential. The Southern Ocean (SO. regulates the Earth’s climate and accounts for 40% of all oceanic carbon cycling. Evidence suggests that microbes are significant mediators in cycling of carbon, nitrogen and sulphur in abyssopelagic ocean through chemo(litho.autotrophic pathways. To investigate this, shotgun metagenome sequences were generated from samples recovered from the abyssopelagic SO. These sequences were assembled and BLASTp performed on translated contigs to assess functional potential and diversity within the metagenomes. Contigs were binned using composition (in.dependent binning approaches and near-complete draft genomes were annotated to assess functional potential. The assembly of 6 datasets produced approximately 39, 000 contigs (?500 bp. per sample. Assemblages were binned to produce 17 bacterial and 14 archaeal genomes. Of these, 13 showed above 40% completeness. BLAST analyses revealed functional dominance of Proteobacteria in all datasets with a high relative abundance (%. of Halobacteria. Further investigation suggests Gamma- and Alphaproteobacteria dominate functional guilds. This contrasts photic ocean zones where Cyanobacteria drive key ecosystem processes. Functional analysis of near-complete draft genomes demonstrated that abyssopelagic microbes have to functional potential for cycling carbon, nitrogen and sulphur through mainly chemoautotrophic pathways. Taken together our results suggest that despite severe micronutrient limitation, high hydrostatic pressure and low mean temperatures of deep-sea environments harbour microbes with surprisingly high metabolic diversity. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.