Distinct and diverse anaerobic bacterial communities in boreal lakes dominated by candidate division OD1

Abstract

Lakes have a central role in the carbon cycle of the boreal landscape. These systems typically stratify in summer and their hypolimnetic microbial communities influence burial of biogenic organic matter in sediments. The composition of bacterial communities in these suboxic habitats was studied by pyrosequencing of 16S rRNA amplicons from five lakes with variable dissolved organic carbon (DOC) concentrations. Bacterioplankton communities in the hypolimnetic waters were clearly different from the surface layer with candidate division OD1, Chlorobi and Bacteroidetes as dominant community members. Several operational taxonomic units (OTUs) affiliated with candidate division OD1 were abundant and consistently present in the suboxic hypolimnion in these boreal lakes. The overall representation of this group was positively correlated with DOC and methane concentrations. Network analysis of time-series data revealed contrasting temporal patterns but suggested similar ecological roles among the abundant OTUs affiliated with candidate division OD1. Together, stable isotope data and taxonomic classification point to methane oxidation and autotrophic denitrification as important processes in the suboxic zone of boreal lakes. Our data revealed that while hypolimnetic bacterial communities are less dynamic, they appear to be more diverse than communities from the oxic surface layer. An appreciable proportion of the hypolimnetic bacteria belong to poorly described phyla.

“Candidatus Sonnebornia yantaiensis”, a member of candidate division OD1, as intracellular bacteria of the ciliated protist Paramecium bursaria (Ciliophora, Oligohymenophorea)

“…These bacteria are usually regarded as being part of the rare biosphere because of their low relative abundance [5,33,56,61]. A recent study, however, revealed that several members of OD1 were abundant and consistently present in the suboxic hypolimnion of boreal lakes [43]. Our study adds to this list with another scenario: a rare taxon of the candidate division OD1 that is sometimes abundant in the cytoplasm of the ciliated protist Paramecium bursaria.…”

“…Ecological and metagenomic data may provide further indications as to the role of the OD1 bacterium in the three-partner consortium. It has been reported that members of the OD1 group are most likely to be anaerobes and may engage in sulfur cycling in various habitats [3,11,16], as well as anaerobic methane oxidation in boreal lakes [43]. A recent metagenomic survey of an acetate-amended aquifer showed that members of OD1 play roles in sulfur cycling and fermentation of refractory sedimentary carbon to produce acetate, ethanol, lactate, and hydrogen [70].…”

Metabolic interdependencies between phylogenetically novel fermenters and respiratory organisms in an unconfined aquifer

“…This finding was later supported by complete genomes for members of SR1, OD1 and WWE3 recovered from acetate-stimulated sediments from this same site (Kantor et al, 2013). These phyla have been identified from non-carbon amended sediments from the same metal-contaminated aquifer and pristine environments (Briée et al, 2007;Peura et al, 2012).…”

Distribution and identity of Bacteria in subarctic permafrost thaw ponds

“…Two ponds, KWK-1 and -12, were typical freshwaters, with low conductivity and warmer surface temperatures in summer, and contained a higher proportion of Betaproteobacteria, typical of freshwater (Hiorns et al 1997, Van der Gucht et al 2005, including a boreal humic lake (Peura et al 2012). Bacteroidetes, related to Sediminibacterium, which is reported to produce H 2 S (Qu & Yuan 2008), were also found in both of these ponds and in KWK-6.…”