title: Metagenomic insights into strategies of aerobic and anaerobic carbon and nitrogen transformation in boreal lakes.
abstract: Thousands of net-heterotrophic and strongly stratifying lakes dominate the boreal landscape. Besides their central role as emitters of greenhouse gases, we have only recently begun to understand the microbial systems driving the metabolic processes and elemental cycles in these lakes. Using shotgun metagenomics, we show that the functional potential differs among lake types, with humic lakes being particularly enriched in carbon degradation genes. Most of the metabolic pathways exhibit oxygen- and temperature-dependent stratification over depth, coinciding with shifts in bacterial community composition, implying that stratification is a major factor controlling lake metabolism. In the bottom waters, rare and poorly characterized taxa, such as ε-Proteobacteria, but also autotrophs, such as photolithotrophic Chlorobia were abundant. These oxygen-depleted layers exhibited high genetic potential for mineralization, but also for fixation of carbon and nitrogen, and genetic markers for both methane production and oxidation were present. Our study provides a first glimpse of the genetic versatility of freshwater anoxic zones, and demonstrates the potential for complete turnover of carbon compounds within the water column.
authors.affiliation: 1] Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, Uppsala, Sweden [2] Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland.
authors.forename: Sari
authors.initials: S
authors.lastname: Peura
authors.affiliation: Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Lucas
authors.initials: L
authors.lastname: Sinclair
authors.affiliation: Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Stefan
authors.initials: S
authors.lastname: Bertilsson
authors.affiliation: Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Alexander
authors.initials: A
authors.lastname: Eiler
mesh_terms: D001420:Bacteria, Aerobic / Q000235:genetics* / Q000378:metabolism; D001421:Bacteria, Anaerobic / Q000235:genetics*; D002244:Carbon / Q000378:metabolism*; D060106:Lakes / Q000382:microbiology*; D056186:Metagenomics / Q000379:methods; D009584:Nitrogen / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D014867:Water / Q000378:metabolism; D014871:Water Microbiology
chemical_list: D014867:Water; D002244:Carbon; D009584:Nitrogen; D010100:Oxygen