Microbial Communities in Ferromanganese Sediments from the Northern Basin of Lake Baikal (Russia)

We analyzed the amplicons of the 16S rRNA genes and assembled metagenome-assembled genomes (MAGs) of the enrichment culture from the Fe-Mn layer to have an insight into the diversity and metabolic potential of microbial communities from sediments of two sites in the northern basin of Lake Baikal. Organotrophic Chloroflexota, Actionobacteriota, and Acidobacteriota, as well as aerobic and anaerobic participants of the methane cycle (Methylococcales and Methylomirabilota, respectively), dominated the communities of the surface layers. With depth, one of the cores showed a decrease in the proportion of the Chloroflexota and Acidobacteriota members and a substantial increase in the sequences of the phylum Firmicutes. The proportion of the Desulfobacteriota and Thermodesulfovibronia (Nitrospirota) increased in another core. The composition of archaeal communities was similar between the investigated sites and differed in depth. Members of ammonia-oxidizing archaea (Nitrososphaeria) predominated in the surface sediments, with an increase in anaerobic methanotrophs (Methanoperedenaceae) and organoheterotrophs (Bathyarchaeia) in deep sediments. Among the 37 MAGs, Gammaproteobacteria, Desulfobacteriota, and Methylomirabilota were the most common in the microbial community. Metagenome sequencing revealed the assembled genomes genes for N, S, and CH₄ metabolism for carbon fixation, and genes encoding Fe and Mn pathways, indicating the likely coexistence of the biogeochemical cycle of various elements and creating certain conditions for the development of taxonomically and functionally diverse microbial communities.