Redox Zone and Trophic State as Drivers of Methane-Oxidizing Bacterial Abundance and Community Structure in Lake Sediments

Eutrophication is expected to increase methane production in freshwater sediments worldwide over the coming decades. Methane-oxidizing bacteria (MOB) consume a significant fraction of this sedimentary methane, but factors that control their distributions and activities are not understood. By combining genetic approaches ( pmo A, 16S rRNA gene, metagenomics) with geochemical sedimentological analyses, we investigate role trophic state, electron acceptors, oxygen (O 2 ) fluxes, potential methylotrophic partner organisms driving distributions, abundances, community compositions MOB across five lakes central Switzerland. Although fluxes were highest eutrophic lakes, methanotrophic abundances peaked oxic anoxic an oligotrophic lake. In all Type I gammaproteobacterial Methylococcaceae dominated suboxic bottom water surface sediments, showing strong correlations putatively Methylophilaceae, whereas II alphaproteobacterial Methylocystaceae increased deeper, sediment layers. Methanotrophic belonging NC10 phylum predominantly detected within denitrifying lake, matching presumed nitrite-dependent lifestyle. While dominant taxa at genus-level follow vertical different aerobic anaerobic respiration reactions, state time deposition was best predictor structure operational taxonomic unit (OTU) level. Elevated combined low moreover, support notion major portion bypasses biological filter escapes overlying water.