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Conversion mechanism of heptachlor by a novel bacterial strain

机译：一种新型细菌菌株对七氯的转化机理

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Microbial treatment is the preferred method for the remediation of soil and water contaminated by heptachlor. We collected sludge samples from the sewage biological treatment pool of Shaanxi Insecticide Factory in Xi'an, China, which were used as bacteria source. With heptachlor as the substrate, at 30–35 °C, an effective microorganism (named strain H) for heptachlor degradation was isolated successfully after a long period of acclimation, screening and purification. Strain H was able to use heptachlor as a carbon source and had a good capacity for biodegradation of heptachlor. Strain H was preliminarily identified as a Gram-negative, short rod-shaped, single-cell bacterial strain that was similar to the genus Escherichia or Shigella, according to the analysis of its morphology and physiological–biochemical characteristics. Then, strain H was further identified as a novel bacterium based on the similarity analysis of its 16S rDNA gene sequence with the sequences logged in the RDP and GenBank databases. The 16S rDNA of this bacterium has never been reported before. When the inoculation volume and the pH were 20% and 7.1–7.6, respectively, the degradation rate of heptachlor can reach more than 88.2% in 130 h, with the initial concentration of heptachlor being 300 μg L ~(?1) at 30–35 °C. Identification of the metabolites by GC/MS showed that strain H degrades heptachlor via two pathways simultaneously, i.e. , pathway (1) hydroxylation at the C1 position of heptachlor to 1-hydroxychlordene followed by epoxidation and dechlorination to chlordene epoxide; and pathway (2) epoxidation at the C2 and C3 positions of heptachlor to heptachlor epoxide, and then heptachlor epoxide was further transformed to chlordene epoxide by dechlorination reaction, or degraded to heptachlor diol by hydrolysis reaction. The biodegradation of heptachlor indicated that heptachlor and its metabolites can be converted into less-toxic small molecular metabolites by a series of reactions such as epoxidation, hydrolysis and dechlorination reactions.
机译：微生物处理是修复被七氯污染的土壤和水的首选方法。我们从中国陕西省杀虫剂厂的污水生物处理池中收集了污泥样本，并将其用作细菌源。以七氯为底物，在30–35°C下，经过长时间的适应，筛选和纯化，成功分离出了有效的降解七氯的微生物（命名为H菌株）。 H菌株能够使用七氯作为碳源，并且具有良好的生物降解能力。根据菌株H的形态和生理生化特征分析，它最初被鉴定为革兰氏阴性，短杆状，单细胞细菌菌株，类似于埃希氏菌属或志贺氏菌属。然后，根据其16S rDNA基因序列与RDP和GenBank数据库中记录的序列的相似性分析，进一步将H菌株鉴定为新型细菌。此细菌的16S rDNA从未被报道过。当接种量和pH分别为20％和7.1–7.6时，七氯的降解率在130 h内可达到88.2％以上，在30–30 h时，七氯的初始浓度为300μgL〜（？1）。 35℃。通过GC / MS鉴定代谢物表明，菌株H同时通过两种途径降解了七氯，即途径（1）在七氯的C1位置羟基化为1-羟基氯烯，然后环氧化并脱氯为环氧氯丙烷;途径（2）在七氯的C2和C3位环氧化为七氯环氧化物，然后通过脱氯反应将七氯环氧化物进一步转化为环氧氯丙烷，或通过水解反应将其降解为七氯二醇。七氯的生物降解表明，七氯及其代谢物可通过一系列反应（如环氧化，水解和脱氯反应）转化为毒性较小的小分子代谢物。

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