Research On Heavy Metal Tolerant Bacteria And Plants Joint Remediation Of Soil Heavy Metal Pollution

In recent years,the combined microbial-plant remediation approach has gradu-ally become a research hotspot in the study of bioremediation of soil heavy metal pollution.Suitable microorganisms can not only promote the growth and develop-ment of plants,but also improve the tolerance of plants to heavy metals,improve the soil microenvironment,and enhance the remediation effect of soil pollution.In this study,we screened the soil microorganisms in the swallow acupuncture mining area at the southern foot of the Qinling Mountains using microbial heavy metal tolerance and plant growth-promoting ability as indicators.The effects of the strains on the physiological indexes and plant heavy metal accumulation of Bidens pilosa L.and alfalfa（Medicago sativa L.）plants under heavy metal stress were studied,and the mechanism of the strains to improve plant heavy metal tolerance was discussed.Fi-nally,suitable plants were selected by measuring the soil heavy metal content and soil enzyme activity under combined remediation.The aim was to discover suitable microbial-plant combinations and provide theoretical support and experimental stud-ies for combined plant-microbial remediation by investigating the effects of heavy metal-tolerant plant-promoting bacteria on plants and combined remediation effects.The main research results are as follows:1.A heavy metal-tolerant strain ZG7 with plant-promoting ability was selected by screening soil microorganisms for heavy metal tolerance and plant-promoting ability at the southern foot of the Qinling Mountains in the Yanzibian mining area.2200 mg/L,500 mg/L,1800 mg/L and 2000 mg/L of Cd²⁺,Cu²⁺,Pb²⁺and Zn²⁺were tolerated by the strain,respectively.16Sr DNA After molecular sequencing,strain ZG7 was identified as Burkholderia sp.The strain ZG7 could grow in the range of p H 5-9,and the growth was slow at temperatures below 25°C.The salt concentration at 0-10 g/L had no effect on the growth of the strain.2.Under heavy metal stress,after inoculation with strain ZG7,the GSH content of Bidens pilosa L significantly increased by 90.7%,SOD and POD activities signif-icantly increased by 82.2%and 156.08%,chlorophyll content significantly increased by 15.76%;dry weight significantly increased by 24.92%compared to uninoculated.Alfalfa MDA content significantly increased by 48.57%,SOD and CAT activities significantly increased by 40.87%and 20.71%,chlorophyll content significantly in-creased by 10.24%;dry weight significantly increased by 27.95%.The inoculation of strain ZG7 could enhance the antioxidant enzyme activity of plants to enhance the heavy metal tolerance of onychomycetes and alfalfa and maintain the growth and development of plants under heavy metal stress.3.Under heavy metal stress inoculation treatment,the Cd content in leaves,Pb content in stems and Zn content in roots of Bidens pilosa L significantly increased by 234.13%,281.53%and 63.38%;Cd content in stems and roots,Pb and Cu content in roots significantly decreased by 33.4%and 63.8%,62.47%and 34.47%,and Zn content in whole plant significantly increased by 11%,and Cd,Pb and Cu content significantly decreased by 41.38%,22%and 27.56%;the enrichment coefficients for Cd and Cu decreased,the transfer coefficients for Cd,Pb and Cu increased,and the transfer coefficients for Zn decreased in Bidens pilosa L.The Zn content of alfalfa roots increased significantly by 17.63%,while the Pb content and Zn content of leaves and the Cd content and Pb content of stems decreased significantly,and the Pb content of the whole plant decreased significantly by 37.84%;the enrichment co-efficient for Pb and the transfer coefficient for Cd,Pb,and Zn decreased.The strain ZG7 could alleviate the toxic effects of heavy metals on plants by changing the en-richment and translocation ability of plants to heavy metals.4.Under heavy metal stress,after the addition of ZG7 bacterial solution,the combination of strain ZG7 and Bidens pilosa L could significantly increase soil cat-alase,sucrase and neutral phosphatase activities;and the combination with alfalfa could significantly increase soil catalase,sucrase,urease and neutral phosphatase ac-tivities compared with the unaddressed treatment.Strain ZG7 can improve soil mi-croenvironment by increasing soil enzyme activity through interaction with plants under heavy metal stress.Through the determination of soil heavy metal content un-der combined remediation,the soil Pb and Zn content was significantly reduced by9.28%and 6.2%when the strain ZG7 was combined with alfalfa compared with sin-gle plant remediation;there was no significant change in soil heavy metal content when combined with Bidens pilosa L.In conclusion,strain ZG7 can improve soil microenvironment by increasing soil enzyme activity through interaction with plants under heavy metal stress.Strain ZG7had more scavenging effect on soil heavy metals when combined with alfalfa.There-fore,the combination of strain ZG7-alfalfa can be given priority in the combined remediation of soil heavy metal pollution in mining areas.