Study On The Synergistic Repair Of Lead-Contaminated Soil By Lead-Tolerant Microorganisms And Landscape Plants

With the rapid development of China’s economy,soil lead pollution has become increasingly prominent,directly affecting agricultural production and food safety.At present,the use of microorganisms combined with phytoremediation of lead-contaminated soils has received increasing attention from the academic community.The metabolic activities of microorganisms and their metabolites can change the soil bioavailability of lead in root soils,thus facilitating the absorption of heavy metals by plants.The existing research mainly focuses on the joint restoration of large herbaceous plants and shrub plants and microorganisms.In this paper,local landscape potted plants are combined with local common microorganisms to repair lead-contaminated soil,providing technical support and accumulation for heavy metal repair.Two strains of resistant strains J1 and J2 were screened from sludge,and their morphology,physiological and biochemical identification and 16SrDNA sequence analysis were carried out.The adsorption characteristics of the strain and its adsorption mechanism were studied.Two dominant plants,pocket coconut and phoenix fern,were selected from landscape plants,and the physiological physiology and lead accumulation characteristics of the two plants were studied.A pot experiment was conducted to study the effects of microorganisms on the lead accumulation of plants under lead stress,and the effects of microorganisms on the physiological and biochemical effects of phytoremediation on soil lead were investigated.The purpose of this study was to investigate the effect of microbial enhancement of phytoremediation and reveal its strengthening mechanism.The main findings are as follows:1.J1 strain with high tolerance to Pb²⁺was selected from the excess sludge.The adsorption rate of J1 strain was 81.25%when the lead concentration was 200mg/L,the Gram staining was negative,the single colony was red,and the colony was Viscous features,flagella,no capsule,no sprouts.The results of physiological and biochemical identification of J1 strain were:glucose fermentation experiment,lactose fermentation experiment,sucrose fermentation experiment,acetylmethylmethanol（VP）experiment,gelatin liquefaction experiment,catalase experiment,esculin hydrolysis test positive;methyl red（MR）,cellulose decomposition test,ethanol oxidation test,starch hydrolysis test,urea hydrolysis test were negative.Combined with morphological observation,physiological and biochemical experiments and16SrDNA sequence analysis,the J1 strain belongs to the genus Serratia marcescens.2.The J2 strain with high tolerance to Pb²⁺was screened out from the excess sludge.The adsorption rate of J2 strain was 73.48%when the lead concentration was200mg/L,the Gram staining was negative,the single colony was yellow,and the colony was It has a rounded bulge,opaque,neat edges,sticky,and extremely flagellate.The physiological and biochemical identification results of J1 strain were:sucrose fermentation experiment,methyl red（MR）,acetyl methyl methanol（VP）experiment,gelatin liquefaction experiment,catalase experiment,starch hydrolysis test,and Qiyeling hydrolysis test were positive;The glucose fermentation experiment,the lactose fermentation experiment,the cellulose decomposition experiment,the ethanol oxidation experiment,and the urea hydrolysis test were negative.Combined with morphological observation,physiological and biochemical experiments and16SrDNA sequence analysis,the J1 strain belongs to Stenotrophomonas pavanii.3.The growth curve of the two strains was determined.J1 strain was in its growth adjustment period from 0 to 24 hours,its growth phase was from 24 to 36hours,its growth period was from 36 to 56 hours,and it entered the decline period after 56 hours.Its growth was the most vigorous.After 72h,the best effect on lead adsorption was 89.6%.J2 strain was in its growth adjustment period from 0 to 5h,its growth phase was from 5 to 36h,and its growth period was from 36 to 60h.After 60h,it entered the decline phase.At 56h,it grew most vigorously.After 96h,the best effect on lead adsorption was 76%.4.The effects of adsorption of Pb²⁺on J1 strain and J2 strain were studied.The results showed that the best conditions for the adsorption of Pb²⁺by the two strains were:pH 7.0 and 9.0,temperature 30°C and 25°C,and the inoculation amount was 5ml.The shaking culture is superior to the static culture,and the inorganic salt type of the medium is NaCl;the medium type is beef extract peptone medium and Chad’s medium.The results of scanning electron microscopy and combined growth curve analysis showed that the adsorption mechanism of J1 strain was surface adsorption,and the adsorption mechanism of J2 strain was surface adsorption and intracellular enrichment.5.Two heavy metal hyperaccumulators of pocket coconut and phoenix fern were selected from the tested landscape plants.After 60 days of culture,the enrichment factors of soil Pb²⁺concentrations of 1500 mg/L and 2000 mg/L were 3.283 and 3.273,respectively.The enrichment factor of P.cerevisiae was 30-90 d when soil concentration was 200-400 mg/L.Between 4.511¹0.819.Both plant enrichment factors are much larger than 1,so they have a good super-enrichment effect.6.Under the lead stress,Serratia and Stenotrophomonas can effectively increase the ability of plants to adsorb Pb²⁺and repair efficiency.The main mechanism is as follows:1.After the soil is connected to the strain,the antioxidant enzyme activity of the plant is increased,and then It alleviates the toxic effect of Pb stress and enhances the tolerance of plants to Pb.2.Soil access to the strain increased the enzyme activity of the roots of the plant to some extent.3.After inoculation,promote the biodiversity of plant root soil,so that the content of bioavailable Pb increases.