Icelandic Lake Targeted Locus (Loci). aquatic metagenome

We present a study of the microbial community in the water column of an Icelandic subglacial lake using multi-locus pyrosequencing libraries, clone libraries, and fluorescent in situ hybridization of cells. The east Skaftárketill lake, maintained by volcanic heat under the Vatnajökull ice cap, is the counterpart to the western lake previously investigated by us. Both lakes are near 4ºC, are anoxic and sulfidic, and have a comparable biomass. Like the west lake, the east lake is dominated by a few bacterial taxa (Acetobacterium, Geobacter, Sulfuricurvum, Sulfurospirillum, and Desulfosporosinus) and there is no evidence for the presence of archaea. The tremendous unevenness of the community prevented our substantial sequencing efforts from fully sampling the community richness. The water column is well-mixed, although some structure is suggested by our data. Clone libraries from enrichment cultures at 3ºC, 60ºC, and 80ºC span a very small fraction of lake diversity but do include Desulfosporosinus and Sulfurospirillum. Not only are the lakes' overall community structures similar, but the same major taxa (≥99% sequence identity) appear in both. This suggests a hydrologic connection, possibly through a subterranean aquifer. The subglacial communities differ markedly from the assemblages in the Kverjkfjöll subaerial lake at the Vatnajökull margin, and a sample of subglacial outburst flood from the lakes. However, they share one major taxon, an epsilon proteobacterium closely related to Sulfuricurvum kujiense, a chemolithotrophic lithoautotrophic sulfur oxidizer. The lake communities may represent a manifestation of a more diverse subterranean biome in the porous volcanic bedrock of Iceland.