Rhizosphere Soil Bacterial Community Composition and Methanotrophic Bacteria is Influenced by Landfill Cover Soil Amelioration

Fertility and oxygen availability in landfill cover soil is a major limitation to the remediation of landfill and activity of methanotrophs as methane oxidation. Sewage sludge compost was used to enhance the landfill cover soil fertilization for landfill revegetation with tolerant plants. In this study, traditional cultivation and modern molecular microbiological techniques were used to detect the ryegrass rhizosphere soil bacterial community composition, soil cultural methanotrphic bacteria and the soil methanotrphic bacteria community composition under the landfill cover soil amended with sewage sludge and sewage sludge compost. The result showed that the biomass were significantly increased by the landfill cover soil with sewage sludge and sewage sludge compost. The polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) analysis showed that, the addition of sewage sludge (SS) or sewage sludge compost (SSC) to the landfill cover plays an important role in improving the rhizosphere soil bacterial community composition. The total number of methanotrophs and MOA in soils stressed by landfill gas could significantly be increased by SS and SSC addition. The result of PCR-DGGE combined 16S rDNA phylogenetic analysis showed that the methanotrophic bacterial community and composition of rhizosphere are obviously influenced by the stress of landfill gas and the addition of SS or SSC to landfill cover soil. The dominant methanotrophic bacteria in landfill cover soil were Methylococcus and Methylobactor which were type I methanotrophic before the stress of landfill gas and ryegrass planting. Nevertheless, the dominant methanotrophic bacteria in rhizosphere soil of ryegrass amended with SSC changed to Methylococcus, Methylocaldum and Methylocystis which were part of Type I methanotrophic bacteria. In contrast, the dominant methanotrophic bacteria in rhizosphere soil of ryegrass amended with SS turned to Methylocaldum, Methylocystis and Methylosinus under this situation and Type II methanotrophic bacteria were more dominant. Therefore, the type of landfill cover amendment has a significant influence on shaping the methanotrophic bacteria community composition and MOA in the rhizosphere soil of the tolerant plants, and the mechanisms may probably be different.