植物抗镉内生细菌筛选及其对小麦幼苗耐镉能力的影响

Screening of cadmium-resistant endophytic bacteria and its effect on enhancing cadmium tolerance of wheat seeding

【目的】筛选出抗镉内生细菌,为应用植物—微生物联合修复技术修复镉污染土壤提供优势菌株。【方法】对秦岭铅锌尾矿区内优势植物杠柳(Periploca sepium Bunge)和草木樨(Melilotus suaveolens Ledeb)的内生细菌进行分离,筛选出具有较高镉抗性的内生细菌,进行16S rDNA序列分析,对其Cd2+去除率、吲哚乙酸(IAA)活性、铁载体活性和1-氨基环丙烷-1-羧酸(ACC)脱氨酶活性等生物学特性进行研究,并利用盆栽试验验证其提高小麦幼苗耐镉胁迫的能力。【结果】在800 mg/L Cd2+浓度条件下共分离筛选得到11株抗镉内生细菌(GS3、CR4、CG7、GR31、GR38、GR42、GR43、GR44、GR45、GR49和GR54),经鉴定均为芽孢杆菌(Bacillus sp.)。生物学特性研究结果表明,在800mg/L Cd2+浓度条件下11株内生细菌的Cd2+去除率在14.56%～79.45%,其中GR44的Cd2+去除率最高;7株内生细菌有IAA活性,其中GR44、GR49和CG7的IAA活性较高;11株内生细菌均有铁载体活性和ACC脱氨酶活性,其中GR44的铁载体活性最高,GR54的ACC脱氨酶活性最高。小麦盆栽试验结果表明,GR44能显著提高小麦幼苗的耐镉能力(P<0.05)。【结论】筛选出的抗镉内生细菌GR44可作为植物—微生物联合修复技术中修复镉污染土壤的优势菌株,对矿区复垦具有一定意义。

【Objective】In order to provide the dominant strains for the remediation of soil polluted by cadmium via plantmicrobe combined remediation system,the cadmium-resistant endophytic bacteria were screened.【Method】Endophytic bacteria were isolated from Periploca sepium Bunge and Melilotus suaveolens Ledeb in Qinling Mountains lead-zinc tailing area,and those with high cadmium-resistant level were screened and identified by analysis of 16S rDNA sequence.The biological characteristics including its removal rate of Cd^2+,the activity of indole acetic acid(IAA),siderophore and 1-aminocyclopropane-1-carboxylic acid(ACC)deaminase were measured.Potted plant experiment was used to test whether the strains improved the tolerance of wheat seeding to cadmium.【Result】The results showed that 11 cadmium-resistant endophytic bacteria(GS3,CR4,CG7,GR31,GR38,GR42,GR43,GR44,GR45,GR49 and GR54)were isolated and screened with the condition of 800 mg/L Cd^2+concentration.All the strains were identified as Bacillus sp.Biological characteristics showed that the removal rate of Cd^2+for all 11 endophytic bacteria were in the range of 14.56%-79.45%at 800 mg/L Cd^2+concentration level,and removal rate of Cd^2+for the strain GR44 was the highest.There were 7 strains which had activity of IAA and strain GR44,GR49,CG7 were higher.All the 11 strains contained siderophore activity and ACC deaminase activity.Siderophore activity of GR44 was the highest,and ACC deaminase activity of GR54 was the highest.Wheat potted experiment showed that endophytic bacteria GR44 could significantly improve the tolerance of wheat seedling to cadmium(P<0.05).【Conclusion】As the selected cadmium-resistant endophytic bacteria,GR44 can be used as dominant strains for constructing the plant-microbe combined remediation system for soil polluted by cadmium,and has positive significance for reclamation of mining area.