镉耐性固定细菌的筛选及其对不同品种小麦镉吸收的阻控效应

Effect of cadmium-tolerant and immobilizing bacteria on cadmium uptake in different wheat cultivars

为筛选重金属耐性固定细菌并探索其阻控小麦对重金属的积累效应,从根际土壤筛选镉耐性固定细菌,研究细菌吸附特性以及细菌对两种小麦Cd含量、富集系数和转移系数的影响。结果表明:筛选到一株镉耐性固定细菌菌株YM4,经16S rDNA序列分析鉴定为假单胞菌(Pseudomonas sp.)。YM4能耐受225 mg·L-1高浓度Cd2+,在含50 mg·L-1Cd2+培养基中对Cd的去除率达到58.9%。YM4对Cd的去除以胞外吸附为主。红外光谱分析发现,细胞壁上参与吸附或结合Cd的官能基团主要有─OH、─NH、羧基和磷酸基团等。小麦盆栽试验中,YM4显著降低小麦地上部(茎叶、麦壳)Cd积累量(11.31%~46.05%和10.12%~42.22%),使籽粒Cd积累量明显下降(26.79%~62.24%,红麦;25.27%~28.99%,白麦)。YM4能显著降低两种小麦茎叶、籽粒和麦壳的Cd富集系数以及籽粒的Cd转移系数。研究表明,镉耐性固定细菌Pseudomonas sp. YM4能降低小麦籽粒Cd含量,阻控小麦对Cd的吸收积累,对中轻度Cd污染土壤的粮食安全生产具有潜在应用价值。

In order to explore the effect of heavy metal-tolerant and-immobilizing bacteria on heavy metal accumulation in wheat,Cd-tolerant and-immobilizing bacteria were screened from rhizosphere soil.The adsorption characteristics and effect of inoculation with the strain on cadmium content,bioaccumulation,and transfer factor in two wheat cultivars were assessed.The results showed Cd-tolerant and-immobilizing bacteria strain YM4,which was identified as Pseudomonas sp.YM4,could grow at high Cd2+concentration(225 mg·L−1)and reduce the concentrations of water-soluble Cd in the solution by 58.9%.Extracellular adsorption was the main mode for Cd removal.Infrared spectrum analysis showed that the functional groups involved in the biosorption process mainly included─OH,─NH,carboxyl groups,and—PO4.In the pot experiment,YM4 significantly reduced the accumulation of Cd(11.31%~46.05%,10.12%~42.22%)in the upper parts of the wheat(straw and husk),especially the grains(red wheat:26.79%~62.24%and white wheat:25.27%~28.99%).YM4 significantly reduced the accumulation coefficients of the straw,grain,and husk as well as the transfer coefficients of the grain in the two wheat varieties.In summary,Cd-tolerant and-immobilizing bacteria Pseudomonas sp.YM4 can reduce the content of Cd in wheat grain,prevent its accumulation in wheat,and provide important bacterial resources for safe crop production in moderately and mildly Cd-contaminated soil.