Comparative metagenomics of coalbed methane microbial communities reveals biogenic methane potential in the Appalachian Basin

Natural gas is a major source of global energy, and a large fraction is generated in subsurface coalbed deposits. Microbial communities within coalbed deposits impact methane production, and as a result contribute to global carbon cycling. The process of biogenic coal-to-methane conversion is not well understood. Here we demonstrate the first read- and assembly-based metagenome profiling of coal-associated formation waters, resulting in the recovery of over 40 metagenome-assembled genomes (MAGs) from eight individual coalbed methane wells in the Appalachian Basin. The majority of samples contained hydrogenotrophic methanogens, which were present in higher relative abundances than was previously reported for other coalbed basins. The abundance of Archaea and salinity were positively correlated, suggesting that salinity may be a controlling factor for biogenic coalbed methane. Low-abundance coalbed microbial populations were functionally diverse, while the most dominant organisms exhibit a high degree of genomic and functional similarities. Basin-specific pan-metagenome clustering suggests lower abundant and diverse bacterial communities are shaped by local basin parameters. Our analyses show Appalachian Basin coalbed microbial communities encode for the potential to convert coal into methane, which may be used as an indicator of potential biogenic methane production for future well performance and increased well longevity.