Study On The Screening Of Zinc-resistanct Strains And The Remediation Of Zn Contaminated Soil By India Mustard Strengthened With The Strains

Soil pollution of heavy metals has become one of the major environmental problems.Phytoremediation for the soil contaminated by heavy metals has become the focus of academic research due to the characteristics of low cost,small disturbance to the soil environment,not causing second pollution and beautifying the landscape.Hyperaccumulator is considered as indispensable material for phytoremediation of heavy metal contaminated soils.However,most hyperaccumulators have the disadvantages of long growth periods and low biomass and low bioavailability of heavy metal in soil,which limits their potential application for contaminated soil severely.In order to improve the efficiency of phytoremediation,inoculation of rhizosphere microorganisms is considered to be an important way to improve the remediation effect of phytoremediation.A strain BC109-2 was isolated from soils which had high level of resistance to Zn and had ability to promote solubilization of insoluble zinc.The tolerant strain was identified as Penicillium janthinellum by morphological and molecular biological identification and named Penicillium janthinellum BC109-2.The minimum inhibitory concentration(MIC)of the strain BC109-2 to zinc reached 2100 mg L-1.The soluble zinc concentration was increased by 113% when cultured shakily for 72 h in the PDB culture medium(containing 1000 mg L-1 ZnCO3).The strain had a strong dissoluting effect on insoluble zinc.The distribution and chemical speciation of zinc in the subcellular fractions were analyzed and the cytotoxicity of the antioxidant system was evaluated on the basis of the screening of BC109-2 with high zinc tolerance and solubility.The zinc content in the cells was proportional to the concentration of zinc in the culture medium.Zn binding to the cell walls was partially proportional(14%-21%)owing to the strong interaction of the anionic cell wall with the metal cations.The cytoplasm and vacuoles(45%-49%)served as another storage compartment for toxins in cells due to the compartmentalization of metals.In addition,most of the zinc of cells existed as insoluble state,oxalate and residual state.The changes of antioxidant enzyme activity under different concentrations of zinc stress demonstrate that adding zinc may lead to oxidative stress in fungal cells.The three kinds of antioxidant enzymes including SOD,CAT,POD directly involved in the process of removing the intracellular production of ROS by coordinating roles,and the content of POD changed most obviously.The GST can catalyze the combination of GSH and hydroxyl radicals,and do not produce GSSG,but its activity had no significant increase.In addition,the activity of GR was decreased due to high concentration of zinc stress,which resulted that the decrease of GSH content more than the increased content of GSSG.In order to enhance the ability of cells to withstand external abiotic stimuli,cells can keep the lipid peroxidation level in a relatively stable level by the comprehensive effect of antioxidant enzymes(SOD,CAT,POD,GR and GST)and the antioxidant enzymes(GSH and GSSG).At last,the index of the plant growth index promoted by strain BC109-2 was evaluated and the effects of the tested strains on the remediation of zinc contaminated soil by India mustard were studied.The strain could produce IAA and siderophore,and have ACC deaminase activity and phosphorus dissolving ability.The strain could promoted the root elongation of Indian mustard.The amount of Zn extracted by the upper part of the India mustard,which was inoculated with the rhizosphere promoting bacteria,increased up 42% compared with the control group.The results indicated that BC109-2 could promote the absorption and enrichment of zinc by India mustard,and it has the potential application in remediation of zinc contaminated soil.