| Phytoremediation is widely used in the treatment of heavy metal pollutions due to its advantages of eco-friendly and simplicity.As a sorts of microbes of bioremediation,endophytes have a high tolerance for heavy metals,which combined with wetland plants improve the environmental quality of water polluted by heavy metals to purify water quality.Therefore,two endophytic strains,Chryseobacterium rhizosphaerae SH-1 and Deftia lacustris SH-2,were used to investigate their application of biological characteristics,application in heavy metal adsorption and plant growth promotion.The main research contents and results were as follows:(1)The strains were analyzed by 16S rDNA extraction,PCR amplification,T3 cloning methods.The strains were Chryseobacterium rhizosphaerae and Delftia lacustris by blast homology comparison,which were named as SH-1 and SH-2,respectively.(2)C.rhizosphaerae SH-1 was mixed with sodium alginate make immobilized pellets to adsorb Cd2+.The removal efficiency was over 93.24%at an initial Cd2+concentration of 100 mg/L,contact time of 480 min and pH of 5.0.The isothermal adsorption characteristics of Cd2+ could be described by Langmuir isothermic adsorption model with the maximum theoretical adsorption capacity of 187.41 mg/g.The pseudo-second-order model well fitted the kinetic process of Cd2+ adsorption by immobilized SH-1 and the theoretical equilibrium adsorption capacity was 51.02 mg/g.The results showed that the immobilized SH-1 had a good effect on Cd2+adsorbing.(3)The tolerance of D.lacustris SH-2 to Pb,Cd,Cu and Ni indicated that it had a high tolerance to Pb2+ and the minimal inhibitory concentration was 1200 mg/L.The surface functional groups and internal structure changes were analyzed before and after Pb2+ adsorbing by SH-2,which found that the protein and lecithin played a significant role in adsorbing Pb2+.What's more,extracellular polymers were observed which combined with lead ions into organic ligand,reducing the harms brought by the lead ions.(4)Effects of indole acetic acid(IAA)and siderophores producing,1-1-amino cyclopropane-carboxylic acid deaminase(ACC)activity and phosphorus dissolving of D.lacustris SH-2 were explored in the study.It found that D.lacustris SH-2 could not dissolve phosphorus which could produce IAA,siderophores and had ACC activity,demonstrating the promotion of SH-2 in palnt growth and then regulate other plant life activities.(5)The reed seedlings cultured by hoagland were used as the control group,and the reed seedlings cultured by hoagland and SH-2 were used as the experimental group.The root length,stem length.accumulation of heavy metal lead.SOD,POD.CAT of reed seedlings were investigated under the different stress concentrations of lead ions.The results found that the measured data of experimental group was higher than that of the control which showed SH-2 could improve resistance of plants to heavy metals.Endophytic bacteria could promote plant growth contaminated with heavy metals.The experiments showed that the synergy of endophytic bacteria and plants had certain feasibility in phytoremediation of heavy metals.In this study,based on plant cell engineering and molecular biology to explore the SH-1 and SH-2 on the heavy metal tolerance and the mechanism of promoting plant grorth,providing theoretical basis for purifying polluted water. |
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