铁氧化菌促进水稻铁膜形成及其对Cd迁移的阻隔

Fe(II)-oxidizing bacterium promotes the formation of iron plaque and the prevention of Cd from soils to rice by iron plaque

通过硫化亚铁梯度管法和邻菲啰啉分光光度法,研究菌株LLDRA6的铁氧化特性。利用扫描电镜-能谱仪(scanning electron microscope-energy spectrum analysis,SEM-EDS)、连二亚硫酸钠-柠檬酸钠-碳酸氢钠(dithionite-citrate-bicarbonate,DCB)法,以及对两种盆栽水稻籽粒和茎叶的Cd含量检测,探讨菌株LLDRA6对IP形成的影响及其对水稻Cd迁移的阻隔效果。研究表明,LLDRA6在硫化亚铁梯度管中形成明显的Fe(II)氧化圈,接种该菌的LB培养基Fe(II)氧化率高于对照组,表明LLDRA6是一株铁氧化细菌。SEM-EDS显示,经LLDRA6和Fe(II)处理后的水稻根系表面附着有明显的层状沉淀物,沉淀物内含有大量Fe元素。DCB法提取试验显示:经LLDRA6和Fe(II)处理后的根系表面IP含量显著高于其他处理组,表明LLDRA6促进了IP的形成;该处理下的茎叶和籽粒的Cd含量均显著低于其他处理组。菌株LLDRA6促进水稻根系表面IP的形成,以及IP对Cd迁移具有显著的阻隔效果。

Through the ferrous sulfide gradient tube and phenanthroline spectrophotometric experiments,the ability of Fe(II)oxidation for strain LLDRA6 was explored.By using methods such as scanning electron microscope-energy spectrum analysis(SEM-EDS),dithionite-citrate-bicarbonate(DCB)extraction test,and the measurement of Cd content in two rice varieties,the effect of strain LLDRA6 on the formation of IP and its effect on the migration of Cd from soils to ricewere discussed.The results showed that strain LLDRA6 formed an obvious Fe(II)oxidation circle in the ferrous sulfide gradient tube.In the presence of strain LLDRA6,the Fe(II)oxidation rate of LB liquid medium was higher than that of LB liquid medium without LLDRA6(the control group),suggesting that this strain was an Fe(II)-oxidizing bacterium(FeOB);SEM-EDS results showed that,after addition of strain LLDRA6 and Fe(II)ions in soils,layered precipitates were formed on the surface of the rice roots,and the energy spectrum analysis(EDS)demonstrated that a large amount of Fe element were contained in these precipitates;the DCB extraction test showed that after treatment with strain LLDRA6 and Fe(II),the Fe content of IP was significantly higher than that of IP formed in other treatment groups,indicating that the strain facilitated the formation of IP.Moreover,the Cd content of the stems,leaves and grains were significantly lower than that of corresponding parts of rice grown in other treatment groups.These results demonstrated that strain LLDRA6 benefited to form IP around rice root surfaces,and the IP had a significant blocking effect on the migration of Cd from soils to rice.