Microbial methane formation in deep aquifers of a coal-bearing sedimentary basin, Germany

Abstract

Coal-bearing sediments are major reservoirs of organic matter potentially available for methanogenic subsurface microbial communities. In this study the specific microbial community inside lignite-bearing sedimentary basin in Germany and its contribution to methanogenic hydrocarbon degradation processes was investigated. The stable isotope signature of methane measured in groundwater and coal-rich sediment samples indicated methanogenic activity. Analysis of 16S rRNA gene sequences showed the presence of methanogenic Archaea, predominantly belonging to the orders Methanosarcinales and Methanomicrobiales, capable of acetoclastic or hydrogenotrophic methanogenesis. Furthermore, we identified fermenting, sulfate-, nitrate-, and metal-reducing, or acetogenic Bacteria clustering within the phyla Proteobacteria, complemented by members of the classes Actinobacteria, and Clostridia. The indigenous microbial communities found in the groundwater as well as in the coal-rich sediments are able to degrade coal-derived organic components and to produce methane as the final product. Lignite-bearing sediments may be an important nutrient and energy source influencing larger compartments via groundwater transport.

Methanogenic Hydrocarbon Degradation: Evidence from Field and Laboratory Studies

“…lack of n -alkanes or changes in biomarker signatures, indicated an extensive biotransformation of oil to methane Jiménez et al, 2012]. Biogenic gas, predominantly deriving from CO 2 reduction, was also predominant in a coal-associated sedimentary basin, as determined by the isotopic signatures (δ 13 C and δD) of CO 2 and methane [Gründger et al, 2015]. Biogenic methane production has also been observed in hydrocarbon-contaminated aquifers after spills or leakage of hydrocarbon-containing waste [Feisthauer et al, 2012].…”

“…A coculture of the n -hexadecane-degrading Desulfatibacillum alkenivorans with a hydrogenotrophic methanogen yielded methane [Callaghan et al, 2012]. Also Desulfatiferula has been identified in methanogenic enrichment cultures [Gründger et al, 2015]. Sulfate reducers in relative high abundance were detected by quantitative PCR of the dsrA genes in the Dagang oil field, which is a low-sulfate environment [Jiménez et al, 2012].…”

“…In the last decades, however, the topic has regained scientific attention and many studies attempting to explain the mechanistic aspects and to identify key microorganisms involved have been conducted. The conversion of hydrocarbons to methane has been extensively demonstrated in laboratory experiments ( table 2 ) Feisthauer et al, 2010;Gray et al, 2011;Gründger et al, 2015;Jiménez et al, 2012;Jones et al, 2008;Siegert et al, 2011;Tan et al, 2013;Wang et al, 2011;Zengler et al, 1999].…”

“…These organisms seem to be involved in the methanogenic degradation of n -alkanes [Zengler et al 1999;Gray et al 2011]. Gründger et al [2015] reported an enrichment of Syntrophaceae (affiliated to the genera Smithella and Desulfomonile ) in methanogenic n -hexadecane-degrading cultures from coal-bearing sediments. Moreover, Gray et al [2011] observed a predominance of Smithella in oil-degrading methanogenic enrichment cultures and its exponential growth in parallel to alkane degradation and methane accumulation, whereas Marinobacter , a known hydrocarbon degrader, did not participate in the biodegradation.…”

“…In summary, in recent years, increasing evidence of the occurrence of in situ methanogenic hydrocarbon degradation has been published Gründger et al, 2015;Jiménez et al, 2012;Jones et al, 2008;Milkov, 2011], reflecting its environmental importance. In addition, laboratory experiments and the extensive use of molecular techniques have contributed to gain information about the methanogenic pathways, the conditions affecting methanogenesis and the microorganisms involved.…”