Insights into coupling between in-situ coalbed water geochemical signatures and microbial communities

Abstract

The degradation of coal into CH4 by microorganisms is a multi-stage process involving a variety of bacteria and archaea. However, little understood about the coupling between in-situ coalbed water geochemical signature and microbial communities involved in different degradation processes. Here, the relation is made between the geochemical signature of the in-situ coalbed water (pH, anions, light metal cations and trace metal elements) and the microbial community (Miquan area, southern Junggar Basin, China). The results show that when the hydrolytic bacteria are the dominant group, they cause an increase in the concentration of certain trace elements in the coalbed water, and different types of hydrolytic bacteria dissolve different types of trace metal elements. Azoarcus and Pseudomonas together dissolve 27 elements including Tl, Sm and Lu. Five trace elements including Nb and V dissolved by Luteolibacter. Even though different hydrolytic bacteria require different Sr concentrations, there is no doubt that hydrolytic bacteria are enriched in Sr-rich environments. As far as methanogenic archaea concerned, Methanobacterium and Methanocorpusculum, which utilize reduced CO2 as a methanogenic pathway, are unaffected by trace metal elements. Although the anions SO42−, NO3− and F− have opposite promoting and inhibiting effects on Methanocorpusculum and Methanobacterium, they do not affect the methanogenic pathway of the microorganisms. Methanothrix increases in relative abundance in low Sr and high Mo concentration and produces CH4 in an acetic acid fermentation pathway. Higher concentrations of the trace elements Cs and Mn increased the relative abundance of Methanolobus, which uses methyl fermentation as the methanogenic pathway. Trace metal elements interactions with bacteria in situ coalbed water and the influence on fluctuations in methanogenic pathways of archaea outweigh other geochemical signatures (pH, anions and light metal cations). This discovery is a significant contribution to the understanding of the interactions between microorganisms and trace metal elements involved in different methanogenic processes in situ coalbed water, and lays the foundation for research on microbial coalbed gas.