Huerta-Cepas, Jaime

AbstractMicrobes in marine sediments play crucial roles in global carbon and nutrient cycling. However, our understanding of microbial diversity and physiology on the ocean floor is limited. Here, we use phylogenomic analyses of thousands of metagenome-assembled genomes (MAGs) from coastal and deep-sea sediments to identify 55 MAGs that are phylogenetically distinct from previously described bacterial phyla. We propose that these MAGs belong to 4 novel bacterial phyla (Blakebacterota, Orphanbacterota, Arandabacterota, and Joyebacterota) and a previously proposed phylum (AABM5-125-24), all of them within the FCB superphylum. Comparison of their rRNA genes with public databases reveals that these phyla are globally distributed in different habitats, including marine, freshwater, and terrestrial environments. Genomic analyses suggest these organisms are capable of mediating key steps in sedimentary biogeochemistry, including anaerobic degradation of polysaccharides and proteins, and respiration of sulfur and nitrogen. Interestingly, these genomes code for an unusually high proportion (~9% on average, up to 20% per genome) of protein families lacking representatives in public databases. Genes encoding hundreds of these protein families colocalize with genes predicted to be involved in sulfur reduction, nitrogen cycling, energy conservation, and degradation of organic compounds. Our findings advance our understanding of bacterial diversity, the ecological roles of these bacteria, and potential links between novel gene families and metabolic processes in the oceans.

Abstract Microbes are the most abundant form of life on Earth and play crucial roles in carbon and nutrient cycling. Despite their crucial role, our understanding of microbial diversity and physiology on the ocean floor is limited. To address this gap in knowledge, we obtained 55 novel bacterial metagenome-assembled genomes (MAGs) from coastal and deep sea sediments. Phylogenomic analyses revealed they belong to four new and one poorly described bacterial phyla. Comparison of their rRNA genes with public databases revealed they are all globally distributed. These novel bacteria are capable of the anaerobic degradation of polysaccharides and proteins, and the respiration of sulfur and nitrogen. These genomes code for an unusually high proportion (~ 9, and up to 20% per genome) of protein families lacking representatives in public databases. Hundreds of these protein families are predicted to be co-localized with genes for sulfur reduction, nitrogen cycling, energy conservation, and the degradation of organic compounds. These findings expand our understanding of microbial diversity and link previously overlooked gene families with key metabolic processes in the oceans.