Who eats what? Unravelling microbial conversion of coal to methane

Abstract

Microbial communities in subsurface coal seams are responsible for the conversion of coal organic matter to methane. This process has important implications for both energy production and our understanding of global carbon cycling. Despite the environmental and economic importance of this process, little is known about which components of the heterogeneous coal organic matter are biodegradable under methanogenic conditions. Similarly, little is known about which taxa in coal seams carry out the initial stages of coal organics degradation. To identify the biodegradable components of coal and the microorganisms responsible for their breakdown, a subbituminous coal was fractionated into a number of chemical compound classes which were used as the sole carbon source for growth by a coal seam microbial community. This study identifies 65 microbial taxa able to proliferate on specific coal fractions and demonstrates a surprising level of substrate specificity among members of this coal-degrading microbial consortia. Additionally, coal kerogen, the solvent-insoluble organic component of coal often considered recalcitrant to microbial degradation, appeared to be readily converted to methane by microbial degradation. These findings challenge our understanding of coal organic matter catabolism and provide insights into the catabolic roles of individual coal seam bacteria.

Subsurface Microbial Invasion Affects the Microbial Community of Coal Seams

“…In parallel, exogenous soil_2 can also potentially affect the decomposition and methane production processes of coal seams. For example, increased Sphingomonadales and Propionibacteriales might participate in the degradation of coal organic matter, and the presence of Rhodocyclales and Nitrosomonadales could enhance acetic acid metabolism . Most interestingly, increased orders of Bacillales and Nitrospirales , are often detected in coal seams and participated in the process of methane production.…”

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

“…These sulfate-reducing bacteria can use kerogen as an end-point autoacceptor or shuttle to oxidize acetic acid or other simple fatty acids, which is the key to the degradation of organic matter in coal seams. 18 Meslé et al. 19 pointed that the depletion of bitumen by solvent extraction resulted in an increase in methane volume in some shales, indicating the methanogenic potential of the shale matrix.…”

Deciphering the initial products of coal during methanogenic bioconversion: Based on an untargeted metabolomics approach

“…To better clarify the specific process of methanogenic coal bioconversion, several studies tried to investigate the interaction mechanism between coal and microbial communities. Vick et al identified the biodegradable components of coal by a native microbial community and the corresponding microorganisms involved in that scenario (Vick et al, 2019). Webster et al evaluated the effect of different chemical oxidative treatments on coal to mimic microbial oxidation, and found that oxidative treatments of coal caused significant changes in chemical profiles compared to untreated coal (Webster et al, 2019).…”

“…), hydrogen, and carbon dioxide, which are then used by methanogens to produce methane (in't Zandt et al, 2017; Wei et al, 2013). The methanogenic coal bioconversion process has important implications for both energy production and our understanding of global carbon cycle (Vick et al, 2019) while a start‐up procedure was necessary and important for the subsequent reactions. The initial stage of coal degradation accounts for great responsibility for the start of bioenergy production and carbon metabolic flux.…”