Study On Tolerance And Quorum Sensing Of Bacteria In Landfill Cover Soil Under Chlorohydrocarbon Stress

Municipal solid waste landfill cover soil is rich in a large number of function microorganisms in the long-term stress greenhouse gases of methane and volatile chlorinated hydrocarbons.So,it was considered to be a good biological catalytic material to remove methane and chlorinated hydrocarbons.Hereby,based on municipal solid waste landfill cover soil,the study carried out the methane oxidation capacity,chlorinated hydrocarbon metabolism ability,microbial diversity analysis,mixed bacteria resistance characteristics and quorum sensing research.The results are as follows:(1)Impact on microbial community structure in presence of physicochemical property and microbial community structure in landfill cover soil(including Laiwu Shandong,Shenzhen Guangdong,Laogang Shanghai and Chang-shengqiao Chongqing municipal solid waste landfill cover soil)as the research object were studied.Representatives of Alphaproteobacteria and Actinobacteria dominated at all four cover soils,ranging from 11.48%~17.40% and 8.97%~14.06%,respectively.And there were strains which could degradation chlorinated hydrocarbons in cover soil.The one of the reasons that impress the variation of cover soils community structure was the difference of total nitrogen,total phosphorus,organic matter,nitrate nitrogen and ammonium nitrogen content.(2)Based on analysis of bacterial community composition in landfill cover soil,methane oxidation ability,trichloroethylene degradation ability and community structure changes were studied.Methane oxidation rate and Trichloroethylene degradation rate range from 0.2~0.87 ?mol/(gsoil·h)and 0.009~0.013 mg/(L·h),respectively.Microbial community structure was changed by the addition of methane and Trichloroethylene,such as Methylophilaceae_uncultured?Pseudomonas and Arthrobacter.It also suggested that there were co-metabolism degradation with non-methane compounds and aerobic assimilation of TCE besides the widely-agreed co-metabolism degradation by methanotrophs.(3)Mixed bacteria were enriched by methane from Chang-shengqiao Chongqing municipal solid waste landfill cover soil.Chlorinated hydrocarbons tolerance and tolerance degree of mixed bacteria in cover soil were studied by tolerance domestication of chlorinated hydrocarbons.The tolerance concentration of mixed bacteria to Dichloromethane,1,2-Dichloroethane,Tetrachloromethane,trans-1,2-Dichloroethylene Trichloroethylene,Tetrachloroethylene,Chlorobenzene and 1,2-Dichlorobenzene are 150 mg/L,140 mg/L,240 mg/L,over 580 mg/L,250 mg/L,500 mg/L,600 mg/L and 500 mg/L,respectively.Chlorohydrocarbon toxicity resist to growth and methane oxidation of bacteria,the greater the concentration,the greater the inhibition.Meanwhile biological dechlorination reaction of Dichloromethane,1,2-Dichloroethane,Trichloroethylene and 1,2-Dichlorobenzene were generated in the process of domestication.(4)Based on the study of chlorinated hydrocarbon tolerance characteristics,the connection between chlorinated hydrocarbon tolerance and quorum sensing was studied from microcosmic aspects.Combining with microbial growth characteristics and microbial community structure,mixed bacteria with the potential of chlorohydrocarbon tolerance were obtained.The mixed bacteria include Methylophilus.Then microbial interactions was analyzed by Pearson correlation index.The result suggested that microbial interactions can affect mixed bacteria of chlorohydrocarbon tolerance and there are Mutual connection and restriction relationship between microbes.Meanwhile,biological metabolic pathways of chlorohydrocarbon was investigated by related gene expression.Particulate monooxygenase was determined as one of the critical enzymes.These implied that chlorinated hydrocarbon degradation in cell contributed to bacteria against toxicity of chlorinated hydrocarbons.