一株溶磷菌对盐地碱蓬修复盐渍土Cd污染的促进效应

为提高盐渍土Cd污染植物修复效率,探讨溶磷菌对盐地碱蓬生长和镉提取效果的影响,采用浸根法收集水培(含2%NaCl)盐地碱蓬的根系分泌物,将其作为唯一碳源培养5株具有Cd活化能力的溶磷菌并依据细菌OD值绘制生长曲线。挑选繁殖速度较快且溶磷和活化Cd能力显著性强(P0.05)的大肠埃希菌(Escherichia)在3个NaCl浓度(0.3、6、12 g·L~(-1))处理下,采用摇瓶实验研究该条件下大肠埃希菌对Ca_3(PO_4)_2和CdCO_3的溶解效应及代谢产物变化。进一步采用Cd平均含量为1.37 mg·kg~(-1)的污灌菜园土,在3个外源NaCl浓度(0、4、8 g·kg~(-1))处理下,利用盆栽实验研究大肠埃希菌对盐地碱蓬修复盐渍土Cd污染的促进效应。结果显示:随盐分增加(0.3、6、12 g·L~(-1)),菌株平均绝对溶磷量(扣除不接菌对照值)分别为80.19、78.79、77.54 mg·L~(-1),平均绝对活化Cd量依次为17.84、17.30、19.73 mg·L~(-1),说明盐分的增加没有阻碍菌株的溶磷功能,且随盐分的增强,可促进Cd的活化。不同盐分下菌株的代谢物组成有明显变化,0.3、6、12 g·L~(-1)盐分处理下菌株分泌的有机酸分别为5、10、13种,分泌的氨基酸分别为4、8、8种。其中缬氨酸的量随盐分增加显著增加(P0.05)。盆栽实验中,4 g·kg~(-1)盐分胁迫下,接菌处理的生物量和根际土壤溶液Cd含量较不接菌对照显著增加(P0.05),Cd总活化量平均增加3.17倍,全量和DTPA提取态Cd富集系数平均提高260%。综上,盐分胁迫下大肠埃希菌可正常生长并促进盐地碱蓬Cd富集。

The promoting effect of phosphorus-solubilizing bacteria on remediation of cadmium-contaminated saline soil by Suaeda salsa

In order to improve the efficiency of phytoremediation on cadmium-contaminated saline soil and to explore the effect of phosphorus-solubilizing bacteria on plant growth and cadmium uptake in contaminated soil, root exudates of Suaeda salsa were collected from a sterile hydroponic(with 2% NaCl) culture. Five cadmium-and phosphorus-solubilizing isolates were cultivated using the exudates as a unique carbon source in medium. Their growth curves were obtained by determining their OD values. Escherichia grew faster and had stronger cadmium-and phosphorus-solubilizing abilities than the rest of the isolates(P<0.05). Herein, its changes in ability to solubilize P and Cd from Ca₃(PO₄)₂ and CdCO₃, respectively, and in its metabolic products in three concentrations of NaCl medium(0.3, 6, 12 g·L^-1) were studied using a shaking flask experiment. A pot experiment was also conducted in sewage-irrigated garden soil(1.37 mg·kg^-1 Cd) pretreated with three concentrations of NaCl(0, 4, 8 g·kg^-1). The promoting effect of Escherichia on remediation of cadmium-contaminated saline soil by Suaeda salsa was investigated. The results showed that Escherichia produced 80.19, 78.79 mg·L^-1, and 77.54 mg·L^-1 dissolved phosphorus and 17.84, 17.30 mg·L^-1, and 19.73 mg·L^-1 dissolved cadmium, respectively, with the 0.3, 6 g·L^-1, and 12 g·L^-1 salt concentration treatments. This shows that an increasing concentration of salt had no effect on P release and promoted Cd release. There was obvious change in the composition of metabolites of Escherichia under the different salt treatments. With the 0.3, 6 g·L^-1, and 12 g·L^-1 salt treatments, 5, 10 kinds, and 13 kinds of organic acids and 4, 8 kinds, and 8 kinds of amino acids were released, respectively. The valine content increased significantly with increasing salt(P<0.05). In the pot experiment, biomass and Cd content in the rhizosphere soil solution of Suaeda salsa with bacterial inoculation treatment increased significantly compared with the control(P<0.05), with 4 g·kg^-1 salt treatment. The total mobilized Cd in the rhizosphere soil increased by 3.17-fold. The average enrichment coefficient of the total and DTPA-extractable Cd increased by 260%. These results suggest that Escherichia grew normally and promoted the accumulation of Cd in Suaeda salsa under salt stress. This study provides some useful information regarding remediation of cadmium-contaminated saline soil.