Characterization of methane, benzene and toluene-oxidizing consortia enriched from landfill and riparian wetland soils

The microbial oxidations of methane (M) and volatile organic compounds (VOCs) were compared with those of M and VOCs alone after enriching soil samples with M and/or VOCs. Landfill cover and riparian wetland soils from which M and VOCs were simultaneously emitted were selected as representative samples. Benzene (B) and toluene (T) were employed as the model VOCs. With the landfill soil consortia, the rate of M oxidation decreased from 4.15-5.56 to 2.26-3.42μmolg-dry soil^-1h^-1 in the presence of both B and T, but with the wetland soil consortia the rate of M oxidation (3.09μmolg-dry soil^-1h^-1) in the mixture of M as well as both B and T was similar to that of M alone (3.04μmolg-dry soil^-1h^-1). Compared with the methanotrophic community with M alone, the portion of type II methanotrophs was greater in the landfill consortia; whereas, the proportion in wetland consortia was less in the presence of both B and T. The oxidations of B and T were stimulated by the presence of M with both the landfill and wetland consortia. There were no correlations between the oxidation rate of M and those of B and T with the gene copy numbers of pmoA and tmoA responsible for the oxidations.