Keystone Microorganisms Regulate the Methanogenic Potential in Coals with Different Coal Ranks

Abstract

Microorganisms are the core drivers of coal biogeochemistry and are closely related to the formation of coalbed methane. However, it remains poorly understood about the network relationship and stability of microbial communities in coals with different ranks. In this study, a high-throughput sequencing data set was analyzed to understand the microbial co-occurrence network in coals with different ranks including anthracite, medium-volatile bituminous, and high-volatile bituminous. The results showed similar topological properties for the microbial networks among coals with different ranks, but a great difference was found in the microbial composition in different large modules among coals with different ranks, and these three networks had three, four, and four large modules with seven, nine, and nine phyla, respectively. Among these networks, a total of 46 keystone taxa were identified in large modules, and these keystone taxa were different in coals with different ranks. Bacteria dominated the keystone taxa in the microbial network, and these bacterial keystone taxa mainly belonged to phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. Besides, the removal of the key microbial data could reduce the community stability of microbial communities in bituminous coals. A partial least-squares path model further showed that these bacterial keystone taxa indirectly affected methanogenic potential by maintaining the microbial community stability and bacterial diversity. In summary, these results showed that keystone taxa played an important role in determining the community diversity, maintaining the microbial community stability, and controlling the methanogenic potential, which is of great significance for understanding the microbial ecology and the geochemical cycle of coal seams.

Improved Formation of Biomethane by Enriched Microorganisms from Different Rank Coal Seams

“…The pH is an important index to respond to the efficiency of anaerobic degradation of bituminous coal. The decrease of pH in the culture solution represents the effective hydrolysis of bituminous coal by microorganisms, and the increase of pH represents the beginning of the production of methane by methanogen using the hydrolysis products . The dynamics of pH in the three experimental groups BC, AC, and CC were relatively similar, all showing a “V” shape (Figure b).…”

“…The decrease of pH in the culture solution represents the effective hydrolysis of bituminous coal by microorganisms, and the increase of pH represents the beginning of the production of methane by methanogen using the hydrolysis products. 25 The dynamics of pH in the three experimental groups BC, AC, and CC were relatively similar, all showing a "V" shape (Figure 1b). The pH in the solution decreased rapidly to 6.11 ± 0.1 from the beginning of the experiment from day 1 to day 5, then showed an increasing trend with the production of methane from day 5 to day 40, and no longer showed significant changes after 40 days.…”