Reductive Dechlorination of TCE by Chemical Model Systems in Comparison to Dehalogenating Bacteria: Insights from Dual Element Isotope Analysis (13C/12C, 37Cl/35Cl)
Reductive Dechlorination of TCE by Chemical Model Systems in Comparison to Dehalogenating Bacteria: Insights from Dual Element Isotope Analysis (13C/12C, 37Cl/35Cl)
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DOI：
10.1021/es400107n
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发表时间：
2013-07-02
影响因子：
11.4
通讯作者：
Elsner, Martin
中科院分区：
文献类型：
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作者：
Cretnik, Stefan;Thoreson, Kristen A.;Elsner, Martin
三氯乙烯（TCE）等氯乙烯类化合物是常见的环境污染物，可通过还原脱氯进行降解.化学模型，如钴胺素（维生素B-12）和其简化的类似物钴肟已被用来模拟微生物还原脱氯。为了测试体外和体内机制是否一致，我们结合了TCE的碳和氯同位素测量。与降解有关的富集因子α（碳）和β（氯）（即，分子平均同位素效应）分别为：对于Geelovleyi菌株SZ为-12.2份/千+/-0.5份/千和-3.6份/千+/-0.1份/千;对于Desulfitobacterium lovniense Y51为-9.1份/千+/-0.6份/千和-2.7份/千+/-0.6份/千;酶辅因子钴胺素为-16.1份/千+/- 0.9份/千和-4.0份/千+/- 0.2份/千;钴肟为-21.3份/千+/- 0.5份/千和-3.5份/千+/- 0.1份/千。双元素同位素斜率m = Δ Δ C-13/Δ Δ Cl-37近似于TCE的δ（碳）/δ（氯），表明生物转化（3.4至3.8）和钴胺素（3.9）之间存在很强的一致性，但对于钴肟（6.1）存在显著差异。这些结果（i）表明尽管微生物菌株不同，但生物降解机制相似，（ii）表明用分离的钴胺素转化类似于体内转化，（iii）表明用钴肟转化的机制不同。因此，应谨慎使用该模型反应物。我们的研究结果表明，二维同位素分析的能力，在全细胞实验和体外模型系统的反应机制的特点和区分。
Chloroethenes like trichloroethene (TCE) are prevalent environmental contaminants, which may be degraded through reductive dechlorination. Chemical models such as cobalamine (vitamin B-12) and its simplified analogue cobaloxime have served to mimic microbial reductive dechlorination. To test whether in vitro and in vivo mechanisms agree, we combined carbon and chlorine isotope measurements of TCE. Degradation-associated enrichment factors epsilon(carbon) and epsilon(chlorine) (i.e., molecular-average isotope effects) were -12.2 parts per thousand +/- 0.5 parts per thousand and -3.6 parts per thousand +/- 0.1 parts per thousand with Geobacter lovleyi strain SZ; -9.1 parts per thousand +/- 0.6 parts per thousand and -2.7 parts per thousand +/- 0.6 parts per thousand with Desulfitobacterium hafniense Y51; -16.1 parts per thousand +/- 0.9 parts per thousand and -4.0 parts per thousand +/- 0.2 parts per thousand with the enzymatic cofactor cobalamin; -21.3 parts per thousand +/- 0.5 parts per thousand and -3.5 parts per thousand +/- 0.1 parts per thousand with cobaloxime. Dual element isotope slopes m = Delta delta C-13/ Delta delta Cl-37 approximate to epsilon(carbon)/epsilon(chlorine) of TCE showed strong agreement between biotransformations (3.4 to 3.8) and cobalamin (3.9), but differed markedly for cobaloxime (6.1). These results (i) suggest a similar biodegradation mechanism despite different microbial strains, (ii) indicate that transformation with isolated cobalamin resembles in vivo transformation and (iii) suggest a different mechanism with cobaloxime. This model reactant should therefore be used with caution. Our results demonstrate the power of two-dimensional isotope analyses to characterize and distinguish between reaction mechanisms in whole cell experiments and in vitro model systems.