Carbon-Nitrogen-Sulfur-Related Microbial Taxa and Genes Maintained the Stability of Microbial Communities in Coals

Coal microbes are the predominant form of life in the subsurface ecosystem, which play a vital role in biogeochemical cycles. However, the systematic information about carbon-nitrogen-sulfur (C-N-S)-related microbial communities in coal seams is limited. In this study, 16S rRNA gene data from a total of 93 microbial communities in coals were collected for meta-analysis. The results showed that 718 functional genera were related to the C-N-S cycle, wherein N₂ fixation, denitrification, and C degradation groups dominated in relative abundance, Chao1 richness, Shannon diversity, and niche width. Genus Pseudomonas having the most C-N-S-related functions showed the highest relative abundance, and genus Herbaspirillum with a higher abundance participated in C degradation, CH₄ oxidation, N₂ fixation, ammoxidation, and denitrification. Such Herbaspirillum was a core genus in the co-occurrence network of microbial prokaryotes and showed higher levels in weight degree, betweenness centrality, and eigenvector centrality. In addition, most of the methanogens could fix N₂ and dominated in the N₂ fixation groups. Among them, genera Methanoculleus and Methanosaeta showed higher levels in the betweenness centrality index. In addition, the genus Clostridium was linked to the methanogenesis co-occurrence network module. In parallel, the S reduction gene was present in the highest total relative abundance of genes, followed by the C degradation and the denitrification genes, and S genes (especially cys genes) were the main genes linked to the co-occurrence network of the C-N-S-related genes. In summary, this study strengthened our knowledge regarding the C-N-S-related coal microbial communities, which is of great significance in understanding the microbial ecology and geochemical cycle of coals.