Biogeographic partitioning of Southern Ocean microorganisms revealed by metagenomics

Abstract

We performed a metagenomic survey (6.6 Gbp of 454 sequence data) of Southern Ocean (SO) microorganisms during the austral summer of 2007-2008, examining the genomic signatures of communities across a latitudinal transect from Hobart (44°S) to the Mertz Glacier, Antarctica (67°S). Operational taxonomic units (OTUs) of the SAR11 and SAR116 clades and the cyanobacterial genera Prochlorococcus and Synechococcus were strongly overrepresented north of the Polar Front (PF). Conversely, OTUs of the Gammaproteobacterial Sulfur Oxidizer-EOSA-1 (GSO-EOSA-1) complex, the phyla Bacteroidetes and Verrucomicrobia and order Rhodobacterales were characteristic of waters south of the PF. Functions enriched south of the PF included a range of transporters, sulfur reduction and histidine degradation to glutamate, while branched-chain amino acid transport, nucleic acid biosynthesis and methionine salvage were overrepresented north of the PF. The taxonomic and functional characteristics suggested a shift of primary production from cyanobacteria in the north to eukaryotic phytoplankton in the south, and reflected the different trophic statuses of the two regions. The study provides a new level of understanding about SO microbial communities, describing the contrasting taxonomic and functional characteristics of microbial assemblages either side of the PF.

Distribution and expression of the cyanate acquisition potential among cyanobacterial populations in oligotrophic marine waters

“…MED4 cynA, suggesting that sequences in this clade are contributed by HL Prochlorococcus clade lacking culture representatives, possibly of the type recently identified with other gene markers (Rusch et al 2010;West et al 2011;Huang et al 2012). Interestingly, we obtained cynA sequences from the Southern Ocean (Table 3), where presence of marine picocyanobacteria has only recently been predicted from metagenome assemblies (Wilkins et al 2012). With the exception of a single sequence, cynA clones from the Amundsen and Bellingshausen Seas clustered with Prochlorococcus sp.…”

Advection shapes Southern Ocean microbial assemblages independent of distance and environment effects

“…Sampling was performed as described in ref. 29, with sites and depths selected to provide coverage of all major SO water masses. At each surface station, E250-560 l of seawater was pumped from E1.5 to 2.5 m depth.…”

“…The exceptions were samples 32 and 33 (49.5°S, 115°E), for which nitrate concentrations were not available, and sample 29 (53.2°S, 115°E) for which phosphate concentration was not available. In these cases, a reading from the appropriate depth was substituted from the nearest available cast (50.0°S, 115°E for samples 32 and 33; 53.8°S, 115°E for sample 29). Pressure values were logðx þ 1Þ QUOTE transformed to reduce right skew 37 , and the combined instrument and hydrochemical data were used to create environmental profiles for each sample.…”

Marine bacterial, archaeal and eukaryotic diversity and community structure on the continental shelf of the western Antarctic Peninsula

“…A few studies have used clone libraries to investigate bacterial diversity, finding high diversity within the Gammaproteobacteria and Cytophaga-Flavobacteria-Bacteroidetes (CFB) divisions (Gentile et al 2006, Piquet et al 2011. More recently, studies have adopted next-generation sequencing approaches to contrast sub-Antarctic and Antarctic bacterial community richness, structure, and biogeography (Ghiglione & Murray 2012, Wilkins et al 2013a.…”