产脲酶细菌矿化修复Cd和Pb污染土壤效应和机制

为了修复重金属污染土壤，保障蔬菜品质安全，利用产脲酶筛选培养基从重金属污染生菜根际土壤中筛选产脲酶细菌.通过溶液吸附和土壤静置培养试验研究功能菌株对Cd和Pb的固定钝化机制；利用水培试验研究功能菌株对不同品种蔬菜生长及吸收Cd和Pb的影响.结果显示，从生菜根际土壤中共分离到10株产脲酶细菌，其中菌株Microbacterium foliorum CH6和Bacillus thuringiensis N3的产脲酶能力（分别为62.6，59.6mS/（cm·min））和吸附钝化Cd和Pb （84.6%~91.3%）的能力最高.扫描电镜-能谱、傅里叶红外光谱和X衍射分析表明，菌株CH6和N3能够通过细胞壁吸附和诱导重金属成矿反应，降低溶液中的Cd和Pb含量.土壤静置试验表明，与不接种菌株对照相比，菌株CH6和N3均能降低土壤中可交态Cd和Pb （46.3%~66.7%）的含量，增加碳酸盐结合态及残渣态Cd和Pb （40%~95.4%）的含量.砂培试验表明，菌株CH6和N3均能显著降低生菜、上海青和空心菜可食用部分中Cd （39.2%~81.4%）和Pb （27.4%~82.3%）的含量.产脲酶细菌CH6和N3能够矿化土壤中的Cd和Pb，降低土壤中重金属有效态含量，阻控生菜、上海青和空心菜对Cd和Pb的吸收.

Effects and mechanisms of urease-producing bacteria mineralization on remediation of Cd- and Pb-contaminated soil

In order to repair heavy metal contaminated soil and ensure the quality and safety of vegetables, the urease-producing bacteria were screened from the vegetable rhizosphere soil by urease-producing medium. The adsorption and immobilization of Cd and Pb by functional strains were studied. Effects of functional strains on the growth and absorption of Cd and Pb by different vegetables were also studied by hydroponic experiment. Ten urease-producing bacteria were isolated from the rhizosphere soil of lettuce. Two strains, Microbacterium foliorum CH6 and Bacillus thuringiensis N3, showed highly ability to producte urease (62.6 and 59.6 (mS/(cm·min), respectively) and immobilize Cd and Pb (84.6%~91.3%). SEM-EDS, FITR and X-ray showed that CH6and N3reduced the content of Cd and Pb in the solution through cell wall adsorption and induced precipitation. Soil static test showed that strains CH6 and N3 reduced the exchangeable contents of Cd and Pb (46.3%~66.7%) and increased the carbonate bound and residual fraction contents of Cd and Pb (40%~95.4%) in soil. A hydroponic experiment showed that, strains CH6 and N3 significantly reduced the Cd (39.2%~81.4%) and Pb (27.4%~82.4%) contents in the edible parts of lettuce, Chinese cabbage and Ipomoea aquatic. Urease-producing bacteria CH6 and N3 could mineralize CD and Pb in soil, reduce the content of available heavy metals in soil, and inhibit the absorption of Cd and Pb by lettuce, Shanghai green and cabbage.