Metagenomic insights into the metabolism of microbial communities that mediate iron and methane cycling in Lake Kinneret iron-rich methanic sediments

Abstract. Complex microbial communities facilitate iron and methane transformations in anoxic methanic sediments of freshwater lakes, such as Lake Kinneret (the Sea Galilee, Israel). The phylogenetic functional diversity these consortia are not fully understood, it is clear which lineages perform reduction anaerobic oxidation (AOM). Here, we investigated from both natural iron-rich (>20 cm depth) iron-amended slurry incubations this zone using metagenomics, focusing on functions associated with cycling. Analyses the indicate that archaea (mainly Bathyarchaeia, Methanomicrobia, Thermoplasmata, Thermococci) bacteria Chloroflexi (Chloroflexota), Nitrospirae (Nitrospirota), Proteobacteria) key metabolic reactions amino acid uptake dissimilation, organic matter fermentation, methanogenesis. Deltaproteobacteria, especially Desulfuromondales (Desulfuromonadota), have potential to transfer electrons extracellularly either mineral particles or syntrophs, including methanogens. This likely via transmembrane cytochromes, outer-membrane hexaheme c-type cytochrome (OmcS) particular, pilin monomers (PilA), all were attributed lineage. Bona fide oxidizers (ANME) denitrifying methanotrophs Methylomirabilia (NC10) may mediate AOM methanogenic sediments; however also consider role methanogens active back flux Putative aerobes, methane-oxidizing Methylomonas their methylotrophic syntrophs Methylotenera, found among slurries involved its intermediates, suggested previously. We propose a reaction model for interactions sediments, linking players interact intricate tradeoffs direct electron between species. Our results highlight complexity an energy-limited environment, where aerobe anaerobe co-exist one strategy survival.