SRA

Lakes and other freshwaters play a crucial role in the global cycling of carbon and associated elements and also provide water for consumption and technical use to society. The microorganisms that inhabit these ecosystems are the key drivers of freshwater biogeochemical processes but our understanding of how individual microbes and microbial groups evolve and contribute to diversity and specific ecosystem functions is incomplete. To help close this knowledge gap we propose sequencing of single-cell amplified genomes (SAGs) from two of the most abundant, yet uncultured, lineages of freshwater bacteria: the Alphaproteobacteria LD12, better known as the freshwater sister group to SAR11, and the Actinobacteria ac1 clade. Both groups are globally distributed and are believed to play major roles in regulating the flux and transformation of carbon and nutrients in lake ecosystems, but the lack of representative genome sequences limits our understanding of these groups. By sequencing multiple representative cells from the ac1 and LD12 clades, including cells collected from geographically separate systems, we can reconstruct the metabolic properties of some of the most successful organisms in freshwater ecosystems. We will also be able us probe the extent of genomic diversification among the LD12 and ac1 groups and increase our understanding of how aquatic bacteria evolve in response to environmental change. Finally, the draft genomes generated from these clades will provide the crucial, but presently missing, “anchors” for metagenomic analyses of freshwater systems that are currently underway.