解磷细菌Klebsiella sp. M2钝化重金属及阻控小麦吸收Cd和Pb效应

Immobilization of Heavy Metals by Phosphorus-solubilizing Bacteria and Inhibition of Cd and Pb Uptake by Wheat

解磷微生物能够将土壤中难溶性的磷转化为可供植物吸收的磷,同时可溶性磷酸盐也能与重金属结合生成沉淀,降低土壤中有效态重金属的含量,进而阻控作物对重金属的吸收,在重金属污染土壤修复中发挥着重要的作用.通过溶液培养试验研究解磷细菌Klebsiella sp.M2固定Cd和Pb以及释放PO43-的规律,并通过盆栽试验探究菌株M2对小麦吸收Cd和Pb的影响及其微生物学机制.结果显示,菌株M2通过细胞壁吸附和诱导磷酸盐沉淀降低溶液中Cd和Pb的浓度,并增加溶液中PO43-的浓度.盆栽试验表明,与不接菌和接灭活菌M2对照相比,接种活菌株M2后能够显著提高(123%~293%)土壤Ca_(2)-P和Ca_(8)-P的含量,降低小麦根际土壤中DTPA-Cd(34.48%)和DTPA-Pb(36.72%)的含量,进而阻控小麦籽粒对Cd和Pb的富集.此外,高通量测序结果表明,菌株M2显著提高了小麦根际细菌群落的多样性,提高了小麦根际土壤中Proteobacteria、Gemmatimonadetes和Bacteroidota的相对丰度,同时增加小麦根际土壤中具有重金属固定和解磷促生特性细菌的相对丰度(主要为Sphingomonas、Nocardioides、Bacillus、Gemmatimonas和Enterobacter),而这些菌属在钝化重金属和阻控小麦吸收重金属的过程中发挥了重要作用.研究结果可为重金属污染农田的生物修复提供菌种资源和理论依据.

Phosphorus-solubilizing microorganisms convert insoluble phosphorus in the soil into phosphorus that can be absorbed by plants.Soluble phosphate combines with heavy metals to form precipitation,reducing the content of available heavy metals,thereby reducing the absorption of heavy metals by crops,which plays an important role in the remediation of heavy metal-contaminated soil.The effects of the immobilization of Cd and Pb and the release of PO43−by the phosphorus-solubilizing bacterium Klebsiella sp.M2 were studied through solution culture experiments.In addition,the effects of strain M2 on wheat uptake of Cd and Pb and its microbiological mechanism were also explored through pot experiments.The results showed that strain M2 reduced the concentrations of Cd and Pb and increased the concentration of PO43−in the solution through cell wall adsorption and induced phosphate precipitation.Pot experiments showed that compared to those in the CK group and inactivated strain M2 group,inoculation with live strain M2 significantly increased(123%-293%)the contents of Ca_(2)-P and Ca_(8)-P in rhizosphere soil,decreased the content of DTPA-Cd(34.48%)and DTPA-Pb(36.72%)in wheat rhizosphere soil,and thus hindered the accumulation of Cd and Pb in wheat grains.Moreover,high-throughput sequencing results showed that strain M2 significantly increased the diversity of wheat rhizosphere bacterial communities;increased the relative abundance of Proteobacteria,Gemmatimonadetes,and Bacteroidota in wheat rhizosphere soil;and increased the proportion of heavy metal-immobilizing and phosphorus-promoting bacteria in wheat rhizosphere soil(mainly Sphingomonas,Nocardioides,Bacillus,Gemmatimonas,and Enterobacter).These bacterial genera played an important role in immobilizing heavy metals and preventing wheat from absorbing heavy metals.These results provide bacterial resources and theoretical basis for the bioremediation of heavy metal-contaminated farmland.