Role Of Plant Growth Promoting Rhizobacteria In Phytoremediation Of Arsenic Contaminated Soils

China has become one of the countries that is affected by arsenic pollution to the upmost extent around the World.Large area of arsenic contaminated field exist in south part of China.Arsenic contamination of soil could result in desolation of the plowland, and damaging human health by food chain.In consideration of China is a leading agricultural nation,arsenic contamination of soil is a big environment problem to be solved urgently.Phytoremediation of arsenic contaminated soils has become a hot research area nowadays and rhizobacteria play an important role during this process.In this study,we screened arsenic resistant bacteria that having plant growth promoting property and apply it to pot experiment in order to investigate its applied portantial in phytoremediation of arsenic contaminated soils.One arsenic resisitant and plant growth promoting bacterium was successfully isolated from rhizosphere of arsenic hyperaccumulated plant Pteris vittata.The 16S rRNA gene sequence of D14 exhibited a 99%identity with a rhizobacterium Agrobacterium tumefaciens NCPPB 2437~T(D14500).The GenBank accession number of its 16S rRNA gene sequence is GQ166481.Assessment of the parameters of plant growth promotion revealed the ability of the strain with the production of indole-acetic acid(IAA) and siderophore:D14 was able to use tryptophan as a precursor to synthesis IAA(7.8 mg/L);D14 excreted sideropores after 2 days cultivation on Chrome azurol S(CAS) plate.D14 also exhibited efficient arsenite oxidation abilities under an aerobic condition with an arsenite oxidation efficiency of 97%after 18 h.Pot experiments were carried out under greenhouse using eggplant as a test vegetable,the pot soil was amended with arsenic to obtain a final concentration of 100 mg/kg,plants were harvested after 3 months growth.Compared to uninoculated plants, D14 enhanced the shoot length,shoot total dry weight and root total dry weight of 1.86, 1.42 and 2.22 folds respectively;increased the unit arsenic concentration(mg/kg) of shoots and roots by of 1.23,2.12 folds respectively;increased the total arsenic content(μg) of shoots and roots by 1.66,4.16 folds respectively.The biomass of roots,total arsenic content of shoots and roots of the plant inoculated with D14 were all significantly increased than the uninocluted plant.The results of pot expriments suggested that D 14 remarkably promoted the growth of eggplant under arsenic stress and decreased the toxicity of arsenic by enlarging plant biamass,which may due to its plant growth promoting property,and increasing the plant accumulation of arsenic at the same time.So we believe that D14 might have some potential to improve phytoextraction efficiency in arsenic contaminated soils.