巨大芽孢杆菌对土壤理化性质及植物富集镉锌的影响

不同生物之间存在复杂相互作用，构建多元生物协同修复有利于提高修复效果.微生物群落繁殖快，适应性强以及抗逆性等优势在土壤重金属污染治理中发挥着重要作用.以巨大芽孢杆菌（Bacillus megaterium）为供试菌株，以包心芥菜［Brassica juncea（L.） Czerniak.］为供试植物，探究二者联合作用下修复Cd和Zn污染土壤的可行性.首先开展60 d室内培养试验，明确巨大芽孢杆菌活化土壤Cd和Zn含量的潜力及改善土壤质量的可行性；进而通过盆栽试验探究巨大芽孢杆菌对包心芥菜富集重金属的影响.结果表明室内培养条件下，巨大芽孢杆菌能够显著降低土壤pH值，土壤有效态Cd和Zn含量显著增加，与对照相比，增幅分别为24%~47%和11%~13%；同时土壤磷酸酶（ALP）、蔗糖酶（SU）和脲酶（UR）活性明显改善.盆栽试验结果表明，与对照相比，接菌处理显著提高了包心芥菜生物量，增幅为10%~23%.同时植物富集Cd和Zn含量升高：植物地上和地下部分Cd富集浓度分别为对照组的1.61~1.70倍和1.05~1.15倍；不同部位对Zn的富集浓度分别为对照的1.38~1.61倍和1.47~1.53倍.相关性分析结果表明，土壤pH值是引起土壤重金属有效态活性和酶活性改变的关键因素.接菌处理下，植物过氧化氢酶（CAT）活性对增强植物抗逆性更为显著.试验结果初步证实了巨大芽孢杆菌-包心芥菜联合修复Cd和Zn污染土壤的可行性.

Effects of Bacillus megaterium on Soil Physicochemical Properties and Its Effects on the Accumulation of Cd and Zn in Plant

The construction of a multi-organism synergistic system is beneficial to improve the effects of remediation because of the complex interaction among different organisms. Microbial communities, with the advantages of fast reproduction, strong adaptability, and stress tolerance, play an important role in the remediation of soil contaminated by heavy metals. Bacillus megaterium and mustard[Brassica juncea (L.) Czerniak.] were chosen to explore the feasibility for the remediation of soil contaminated with Cd and Zn. The results of the 60d indoor culture experiment showed that the soil pH value was significantly (P<0.05) reduced by Bacillus megaterium compared with that in the control. The available contents of Cd and Zn were significantly (P<0.05) increased by 24%-47% and 11%-13%, respectively. Meanwhile, the activities of soil alkaline phosphatase (ALP), sucrase (SU), and urease (UR) were improved considerably. Compared with that in the control, the addition of Bacillus megaterium significantly (P<0.05) increased the biomass of the plant by 10%-23%. At the same time, the contents of Cd in the aboveground parts and roots of the plants were increased by 1.61-1.70 and 1.05-1.15 times than the control values and by 1.38-1.61 and 1.47-1.53 times for Zn contents, respectively. The inoculation of Bacillus megaterium significantly enhanced the activities of antioxidant enzymes in the plant. The subsequent correlation analysis suggested that soil pH was the key factor leading to changes in the availability of heavy metals and soil enzyme activities.Catalase (CAT) was the most significant antioxidant enzyme type that improved the resistance and growth of the plant under the heavy metal stress. This study preliminarily confirmed the feasibility of the combination of Bacillus megaterium and mustard for the remediation of soil contaminated with Cd and Zn.