Page 89 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Figure 1. Monthly methane quantity and acetate concentration measurements in the amended coal well (A) and total cell count data for both the nutrient/acetate amended and the control coal well (B). No methane production was observed in the control coal well. To the amended coal well, 10 mM acetate was added at 0 and 4 months, respectively. A) open squares (£), acetate concentration in mM; filled squares (¢), total methane in mmol; B) open squares (£), total cell count in cells ml-1 for the nutrient/acetate amended well; filled squares (¢), total cell count in cells ml-1 for the control well.
In the metagenome, we found functional genes encoding lignin, manganese and versatile peroxidases that are involved in complex organic compound degradation. Even though these enzymes require oxygen as co-substrate, Agaricomycetes have been previously detected in several anoxic environments such as marine ecosystems (reviewed by Manohar and Raghukumar, 2013), anoxic organic carbon-rich mangrove soils (Arfi et al. 2011) and anoxic freshwater sediments (Zhang, Huang and Chen 2015). This suggests that extremely low oxygen concentrations possibly penetrating into anoxic habitats can still support such enzyme activities. Agaricomycetes are the only class of fungi capable of substantial lignin degradation (Floudas et al. 2012), which supports their potential role in the breakdown of lignin-derived structures in coal as has been showed for filamentous fungi (Hofrichter, Bublitz and Fritsche 1997).
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