镉吸附细菌的分离及其对土壤镉的固定

目的] 探究镉吸附细菌是否能够高效固定土壤有效镉（Cd），为土壤有效Cd的微生物固定提供理论依据。方法] 利用含Cd²⁺牛肉膏蛋白胨液体培养基对细菌进行Cd的耐受性测试筛选出镉抗性强的菌株；通过16S rRNA基因相似性及系统进化分析鉴定耐镉细菌，将菌细胞加入含CdCl₂溶液中进行Cd²⁺吸附效率测定；通过土培模拟实验，测定土壤pH、碱解氮、有效磷、速效钾、有机质、CEC、有效Cd及微生物数量来分析镉吸附细菌对镉污染土壤的影响。结果] 从德阳鱼腥草根际土壤中分离获得的57株细菌对Cd²⁺表现出不同程度的抗性，并从中筛选出3株耐Cd优势细菌普罗威登斯菌属（Providencia）DY8、芽孢杆菌属（Bacillus）DY3和芽孢杆菌属（Bacillus）DY1-4。其对溶液中的Cd²⁺表现出较好的吸附作用，吸附效率随着Cd²⁺浓度升高而降低。DY8、DY3、DY1-4能使镉污染土壤中有效Cd含量分别降低72.11%、68.55%、62.32%，同时显著提高镉污染土壤中碱解氮、有效磷的含量。结论] Cd污染农田土壤中含有丰富的耐Cd微生物资源，Cd吸附细菌能降低土壤中有效Cd的含量，且能有效改善土壤养分条件。

Isolation of cadmium-adsorbing bacteria for soil cadmium fixation

Objective] To study Cd-adsorbing bacteria for fixing soil Cd. Methods] Tolerance of microbe against Cd was measured in the beef extract peptone liquid medium containing Cd²⁺ to select cadmium-resistant strains. The cadmium-tolerant bacteria were identified by 16S rRNA gene similarity and phylogenetic analysis, The adsorption efficiency of bacteria for Cd²⁺ was determined by adding bacteria cells into the solution containing CdCl₂. Soil culture simulation experiment was performed to analyze the effects of cadmium adsorption bacteria on cadmium-contaminated soil by determining soil pH, alkali-hydrolyzed nitrogen, available phosphorus, available potassium, organic matter, CEC, available Cd and the number of microorganisms. Results] Total of 57 bacteria strains isolated from the rhizosphere soil of Houttuynia cordata at Deyang showed different degrees of resistance to Cd²⁺. Three dominant Cd-resistant bacteria strains were Providencia DY8, Bacillus DY3 and Bacillus dy1-4. They showed good adsorption efficiency to Cd²⁺ in liquid. The adsorption efficiency of Cd²⁺ decreased with the Cd²⁺ concentration increasing. DY8, DY3 and DY1-4 reduced the effective Cd content in cadmium-contaminated soil by 72.11%, 68.55% and 62.32%, respectively, and significantly increased the alkali-dissolved nitrogen and available phosphorus in cadmium-contaminated soil. Conclusion] The Cd-contaminated farmland soil contains rich resources of Cd-resistant microorganisms. Cd-absorbing bacteria can reduce the content of effective Cd in soil and improve soil nutrient conditions.