Microbial community succession between coal matrix and culture solution in a simulated methanogenic system with lignite

The enhancement of coalbed methane generation by microorganisms has raised global interests in the passing two decades. Methane production with coal involves many different types of microbes' synergism. In this study, we investigated the microbial distribution characteristics in a biogas generation system with Shengli lignite. Archaeal and bacterial communities in the coal matrix and culture solution were investigated over time by high-throughput sequencing methods. The results showed that bacterial diversity was higher than the archaea in all samples. It appears that almost all archaea were assigned to the phylum Euryarchaeota. Methanosarcina was the most abundant methanogen. The bacteria in all samples were assigned to 12 phyla and 88 genera. Firmicutes were the most abundant phylum. Although the community structure of archaea changed with the sampling time during the biogas generation from 20 to 40 days, the distribution was similar between coal matrix and solutions, suggesting the sampling sources (phases) had limited impacts on the distribution pattern. However, the bacterial communities were greatly influenced not only by sampling time but also by the sampling sources as the bacteria have greater diverse metabolic pathways. The degree of differences in the distribution of bacteria was higher than that of archaea. The phyla of Spirochaetae and Actinobacteria were the most important bacteria contributing to the main differences between the solution and coal. By analyzing the growing tendency of microbes in coal and/or solution, substrates utilization characteristics might play an important role in the growing tendency of bacteria. As for archaea, the syntrophic association and aggregation with bacteria might be the main factors. The present work provides a new insight for investigating the microbial functions in biogenic methane systems. This information can be used for the selection of microbial consortia and regulating methods for the enhanced production of coalbed methane.