The Heavy Metal Immobilized Bacterial Community Composition And Its Function On Reducing Heavy Metal Accumulation In Xinxiang City Cadmium-contaminated Farmland Soil

Over the years,with the rapid development of economic,large amount of farmland in China have been seriously polluted by heavy metals,of which cadmium(Cd)pollution is the most serious.Heavy metal pollution in soil will destroy the original stable microbial community structure and diversity,which in turn affects soil fertility,so it is urgent to repair it.In recent years,there are three main technologies for remediation of land contaminated by heavy metals: physical,chemical and biological.The microbial community in the soil contaminated by heavy metals is very rich and is the important source of microbial resources for bioremediation.In this paper,cadmium(Cd)contaminated soil is taken as the object of research.The soil samples were taken from three sampling sites near a battery factory in Xinxiang City,Henan Province.After the samples were brought back to the lab,determine the content of heavy metals Cd in three soil samples.Extracting the total DNA of the soil for high-throughput sequencing and microbial plate culture method to analyze the bacterial community composition of the soil sample.The Cd shaking flask adsorption experiment for the strains isolated by the cultivable method was used to screen out the strains with good Cd fixation effect.The strain was further verified by the pot experiment of green vegetable.The green vegetable variety was chicken cabbage.With a view to screen out efficient strains that could both reduce Cd content in different tissues of root,stem and leaf of green vegetables and also improve the biomass of green vegetables,to provide species resources for bioremediation of heavy metal contaminated soil in Xinxiang city,and to provide reference basis for studying the composition and function of the bacterial community in heavy metal contaminated soil.The main findings are as follows:1.The extraction of total soil DNA and high-throughput sequencing showed that it consists of 25 phyla and 400 genera,25 phyla are Actinomycetes,Proteobacteria,and Acidobacteria,400 species are sphingosine Alcohols,Nitrospira,Skermanella,etc.A total of 159 strains were isolated from heavy metal contaminated soil collected from three sampling points in Xinxiang City by traditional plate lineation separation method,16 S rRNA sequencing and homology comparison showed that the isolated strains consisted of 4 phyla and 30 genera,4 phyla included Actinomycetes,Bacteroides phylum,Paecilomycetes and Proteobacteria,and 30 genera included Bacillus,Rhizobia and Arthrobacter etc;Comparing the results obtained by high-throughput sequencing with traditional plate lineation separation method,the former has a richer community composition.Through the analysis of molecular ecological network of high-throughput sequencing showed that the key bacteria were Arthrobacter,Ferruginibacter,Flavitalea,Marmoricola,Nitrospira,Nocardioides,Lysobacter and so on.2.The Cd fixation and adsorption abilities experiments showed that 30 strains of 11 genera included Aneurinibacillus,Arthrobacter,and Bacillus have good fixing effect.The effect verification experiment showed that six high-efficiency strains such as Agrobacterium sp.(1-3),Ochrobactrum sp.(1-6),Bacillus sp.(2-12)can both reduce Cd in different tissues of rhizomes and leaves also can increase the biomass of green vegetables.