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首页> 外文期刊>Environmental toxicology and chemistry >SIMULTANEOUS DETERMINATION OF MERCURY METHYLATION AND DEMETHYLATION CAPACITIES OF VARIOUS SULFATE-REDUCING BACTERIA USING SPECIES-SPECIFIC ISOTOPIC TRACERS
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SIMULTANEOUS DETERMINATION OF MERCURY METHYLATION AND DEMETHYLATION CAPACITIES OF VARIOUS SULFATE-REDUCING BACTERIA USING SPECIES-SPECIFIC ISOTOPIC TRACERS

机译：使用特殊同位素示踪剂同时测定各种硫酸盐还原菌的汞甲基化和脱甲基能力

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The use of species-specific isotopic tracers for inorganic and methyl mercury has allowed the simultaneous determination of the methylation and demethylation potentials of pure culture of isolated sulfate-reducing (SR) bacterial strains using low Hg species concentration levels (7 μg/L ~(199)Hg(II), 1 μg/L Me~(201) Hg). A major advantage of the method reported here is that it can be used to follow simultaneously both the degradation of the species added but also the formation of their degradation products and thus the determination during the same incubation of the specific methylation/demethylation yields and rate constants. Methylation/demethylation capacities and extents have been found to differ between the tested strains and the tested conditions. The methylating/demethylating capacities of bacteria appear to be strain specific. All the methylating strains were found to demethylate methylmercury (MeHg). The active mechanism responsible for Hg methylation appears directly dependent on the bacterial activity but is not dependent on the metabolism used by the tested bacteria (sulfate reduction, fermentation, or nitrate respiration). The results provide confirmation that SR strains contribute to MeHg demethylation under anoxic conditions, leading to Hg(II) as the end product, consistent with the oxidative degradation pathway. Kinetic experiments have allowed specific transformation rate constants to be addressed for the two reversible processes and the reactivity of each isotopic tracer to be compared. The differential reactivity highlighted the different steps involved in the two apparent processes (i.e., uptake plus internal transformation of mercury species). Methylation appears as the slowest process, mainly controlled by the assimilation of Hg(II), whereas demethylation is faster and not dependent on the MeHg concentration.
机译：对无机汞和甲基汞使用物种特异性同位素示踪剂，可以同时测定低汞含量（7μg/ L〜（）的分离硫酸盐还原（SR）细菌菌株纯培养物的甲基化和去甲基化潜力。 199）Hg（II），1μg/ L Me〜（201）Hg）。此处报道的方法的主要优势在于，它既可以用来同时追踪所添加物种的降解，也可以用来追踪其降解产物的形成，从而可以同时追踪特定甲基化/去甲基化产率和速率常数的测定。已经发现甲基化/脱甲基化能力和程度在测试菌株和测试条件之间是不同的。细菌的甲基化/去甲基化能力似乎是菌株特异性的。发现所有甲基化菌株均使甲基汞（MeHg）脱甲基。导致汞甲基化的活性机制似乎直接取决于细菌的活性，但并不取决于所测试细菌所使用的代谢（硫酸盐还原，发酵或硝酸盐呼吸）。结果提供了证实，SR菌株在缺氧条件下有助于MeHg脱甲基，从而导致Hg（II）作为最终产物，与氧化降解途径一致。动力学实验允许解决两个可逆过程的特定转化率常数，并比较每个同位素示踪剂的反应性。反应性的差异突出了两个表观过程中涉及的不同步骤（即汞的吸收和内部转化）。甲基化似乎是最慢的过程，主要由Hg（II）的同化作用控制，而脱甲基化则更快，并且不依赖于MeHg浓度。

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