Novel Chemolithotrophic And Anoxygenic Phototrophic Genomes Extracted From Ice-Covered Boreal Lakes

Although an important fraction of the worlds lakes remains ice-covered during a large proportion of the year, little is known about the microorganisms that govern the biogeochemical processes occurring under-ice along the stratigraphic redox gradients. Reconstructed genomes provide evidence for anoxygenic photosynthesis involving fixation of carbon using reduced sulphur and iron as an electron donor in the anoxic zone of the sampled lake systems. In addition to anoxygenic photosynthesis, our molecular data reveals novel chemolithoautotrophic organisms and supports the existence of methanotrophs in bottom anoxic waters. Reconstructed genomes matched methanotrophs related to Methylobacter tundripaludum, phototrophic Chloroflexi and Chlorobia, as well as lithoautotrophic genomes affiliated to the Betaproteobacteria class and Planctomycetes phylum. Based on our in-depth characterization, complex metabolic interactomes emerge unique to each lakes redox tower and with sulfur, iron and carbon cycling tightly intertwined through chemolithotrophy and anoxygenic photosynthesis.