Comparison of RNA- and DNA-based bacterial communities in a lab-scale methane-degrading biocover

Methanotrophs must become established and active in a landfill biocover for successful methane oxidation. A lab-scale biocover with a soil mixture was operated for removal of methane and nonmethane volatile organic compounds, such as dimethyl sulfide (DMS), benzene (B), and toluene (T). The methane elimination capacity was 211 ± 40 g m^-2 d^-1 at inlet loads of 330-516 g m^-2 d^-1. DMS, B, and T were completely removed at the bottom layer (40-50 cm) with inlet loads of 221.6 ± 92.2, 99.6 ± 19.5, and 23.4 ± 4.9 mg m^-2 d^-1, respectively. The bacterial community was examined based on DNA and RNA using ribosomal tag pyrosequencing. Interestingly, methanotrophs comprised 80 % of the active community (RNA) while 29 % of the counterpart (DNA). Types I and II methanotrophs equally contributed to methane oxidation, and Methylobacter, Methylocaldum, and Methylocystis were dominant in both communities. The DNA vs. RNA comparison suggests that DNA-based analysis alone can lead to a significant underestimation of active members.