Microbial community structure and metabolic potential of chronically polluted coastal sediments from cold regions of the northern and southern hemispheres

DIONISI, H. M.; LOZADA, M.; MAC CORMACK, W.; CARROLL, J.; LUNDGREN, L; SJÖLING, S. ; CHAVARRÍA, K.; MASON, O.; JANSSON, J.

Mar del Plata

Congreso; VIII Congreso de Microbiología General; 2012

Sociedad Argentina de Microbiología General

Although environmental microorganisms have a decisive role in ecosystem functioning, the underlying mechanisms shaping microbial communities and establishing their biogeographic patterns are still poorly understood. With the goal of increasing our understanding of the biogeographic distribution and functional traits of microorganisms from cold, polluted coastal sediments, we are performing a comprehensive characterization of the structure and function of microbial communities from sediments of four hydrocarbon-polluted cold regions (Potter Cove, Antarctic Peninsula; Ushuaia Bay, Tierra del Fuego Island; Värtahamnen, Baltic Sea; Adventfjord, Svalbard Archipelago). This project is the result of an international collaboration between researchers of Argentina, USA, Sweden and Norway, and has been funded by the Community Sequencing Program of the Joint Genome Institute (JGI-DOE, USA).Microbial community structure is being analyzed by sequencing 16S/18S rRNA gene amplicons using both 454-Titanium and Illumina platforms (pyrotags and i-Tags, respectively). Up to date, we have analyzed pyrotags from 18 sediment samples of three regions (Potter Cove, Ushuaia Bay and Baltic Sea, approximately 250,000 reads). The two Southern Hemisphere regions were homogeneous both in diversity and composition, but showed significantly lower diversity and different composition than the Baltic Sea communities. Flavobacteria, Gammaproteobacteria, Deltaproteobacteria and protists (Alveolata, Stramenopila) were abundant in all samples. However, Deltaproteobacteria associated with sulphate reduction were significantly more abundant in the South Hemisphere sites, while Betaproteobacteria, Anaerolineae and methanogenic Archaea were distinctive of the low salinity Baltic Sea samples, indicating differences in carbon cycling in these two different environment types.The metabolic potential of the microbial communities is being analyzed by metagenomic shotgun sequencing. Approximately 7 billion reads have been generated using an Illumina HiSeq platform with 2 x 151 bp cycles. On average, 17% of the reads were able to be mapped to assembled contigs 0.8 to 100 Kb in length. In accordance with pyrotag analysis, the taxa most frequently identified in the sediment metagenome were Flavobacteria, Deltaproteobacteria and Gammaproteobacteria. Megablast analysis showed a high number of contigs related to genome sequences from the sulfate-reducing hydrocarbon degraders Desulfatibacillum alkenivorans AK-01, Desulfococcus oleovorans Hxd3, Deltaproteobacterial strain NaphS2, as well as the enrichment culture N47. We will further use the deep metagenomic sequencing data to identify key environmental components that contribute to the selection of particular genetic traits, to infer how pollution affects microbial services, and to analyze the diversity, functional redundancy and biogeography of hydrocarbon biodegradation genes and pathways.