• 关键词：土生拉乌尔菌  氧气浓度  汞甲基化  三峡库区  消落带土壤  分离  鉴定

• 基金项目：国家自然科学基金（No.41573104，41773073，41877384）

• 米前芬
• 西南大学资源环境学院, 重庆 400716

• 向玉萍
• 西南大学资源环境学院, 重庆 400716

• 王永敏
• 重庆市三峡库区农业面源污染控制工程技术研究中心, 重庆 400716

• 陈华
• 西南大学资源环境学院, 重庆 400716

• 曹丹
• 西南大学资源环境学院, 重庆 400716

• 王定勇
• 1. 西南大学资源环境学院, 重庆 400716;2. 重庆市三峡库区农业面源污染控制工程技术研究中心, 重庆 400716

• 申鸿
• 1. 西南大学资源环境学院, 重庆 400716;2. 西南大学前沿交叉学科研究院生物学研究中心, 重庆 400716

• 摘要：从三峡库区消落带土壤中分离、纯化得到1株具有汞甲基化能力的细菌，对其形态、生理生化特征及16S rRNA基因序列进行分析后，鉴定为土生拉乌尔菌，并命名为RaouLtella terrigena TGRB3.研究发现，菌株TGRB3具有强酸碱和盐度适应能力，为中高温型菌，在pH=4~9和盐度0.2%~4.0%范围内均能正常生长，最适生长温度为25℃.在Hg²⁺浓度为1000 μg·L^-1时，菌株生长受到显著抑制.此外，在初始Hg²⁺浓度为300 ng·L^-1的条件下探讨了该菌在不同氧气浓度（0、7%、14%和21%）下的生长情况及汞甲化能力.结果表明，该菌的生长不受氧气浓度的制约，但在有氧条件下生长更好，且在厌氧或低氧浓度条件下具有更强且稳定的汞甲基化能力.在氧气浓度为14%和21%的条件下，该菌的最大甲基汞含量分别为（0.54±0.01）和（1.62±0.08）ng·L^-1，试验后期表现出较强的去甲基化现象，培养54 h后的甲基汞含量显著降低为（0.08±0.02）和（0.05±0.00）ng·L^-1；而在氧气浓度为0和7%的条件下，最大甲基汞含量分别为（6.75±1.75）和（3.24±0.74）ng·L^-1，且在试验周期内甲基汞持续产生，平均浓度分别为（3.23±1.39）和（1.66±0.71）ng·L^-1.本试验结果可望为三峡库区消落带土壤汞生物甲基化机理的深入研究及汞污染风险评价等提供全新的试验材料.

• Abstract：A bacterial strain capable of Hg methylation was isolated from the soil of the water-level-fluctuation-zone (WLFZ) of the Three Gorge Reservoir, in Shibaozhai, Zhongxian Country, Chongqing, Southwest China. Through morphological and physiological characterization, and 16S rRNA gene sequence analysis, this isolate was identified as RaouLtella terrigena sp. and named as R. terrigena TGRB3 (accession number:MK102091). Strain TGRB3 has strong acid-base and salinity tolerance, and could survive under pH from 4 to 9, and 0.2%~4.0% of salinity. It is a mesophilic strain, with the optimum growth temperature of 25℃. When Hg²⁺ concentration was 1000 μg·L^-1, the growth of strain TGRB3 was significantly inhibited. In addition, its Hg methylation ability under different oxygen concentrations (0, 7%, 14% and 21%) was studied at the initial Hg²⁺ concentration of 300 ng·L^-1. Results show that the growth of strain TGRB3 was not restricted by oxygen concentration, but grew better under aerobic conditions. Besides, it had a stronger and more stable Hg methylation ability under anaerobic and low oxygen concentration. Under the oxygen concentration of 14% and 21%, the maximum MeHg levels were (0.54±0.01) and (1.62±0.08) ng·L^-1, which decreased significantly to (0.08±0.02) and (0.05±0.00) ng·L^-1 at the 54 h, respectively. When the oxygen concentration was 0 and 7%, MeHg were produced continuously during the whole incubation period, reaching the maximum MeHg levels at (6.75±1.75) and (3.24±0.74) ng·L^-1, respectively, and (3.23±1.39) and (1.66±0.71) ng·L^-1, in average. This study might be expected to provide new experimental data for in-depth study of the Hg bio-methylation mechanism and the risk assessment of Hg pollution in the WLFZ of the Three Gorge Reservoir.

• Key words：RaouLtella terrigena  oxygen concentration  mercury methylation  Three Gorge Reservoir  water-level-fluctuation-zone  isolation  identification

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