Comparison of RNA- and DNA-Based Bacterial Communities in a Lab-Scale Methane-Degrading Biocover using Ribosomal Tag Pyrosequencing. biofilm metagenome

Methanotrophs must become established and active in landfill biocover for successful methane oxidation. A lab-scale biocover with a soil mixture (soil:granular activated carbon:earthworm cast:saprolite=4:1:1:1, w/w) was operated for removal of methane and non-methane volatile organic compounds such as dimethyl sulfide (DMS), benzene (B) and toluene (T). 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. Bacterial community was examined based on DNA and RNA using ribosomal tag pyrosequencing. Interestingly, methanotrophs comprised 80% in the active community (RNA), while 29% in the counterpart (DNA). Types I and II methanotrophs equally contributed to the 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.