Identification of the hcb gene operon involved in catalyzing aerobic hexachlorobenzene dechlorination in Nocardioides sp. strain PD653.
Identification of the hcb gene operon involved in catalyzing aerobic hexachlorobenzene dechlorination in Nocardioides sp. strain PD653.
复制标题
诺卡氏菌中参与催化好氧六氯苯脱氯的 hcb 基因操纵子的鉴定。
DOI：
10.1128/aem.00824-17
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发表时间：
2017
影响因子：
4.4
通讯作者：
Fabrice Martin-Laurent and Shizunobu Igimi
中科院分区：
文献类型：
--
作者：
Koji Ito;Kazuhiro Takagi;Akio Iwasaki;Naoto Tanaka;Yu Kanesaki;Fabrice Martin-Laurent and Shizunobu Igimi
Nocardioides sp.菌株PD653是第一个被发现的能够矿化六氯苯（HCB）的好氧细菌。在本研究中，从菌株PD653的传代培养中意外分离出的菌株PD653- b2被发现缺乏将HCB或五氯硝基苯转化为五氯苯酚的能力。对比分析发现，菌株PD653- b2发生了基因重排，缺失了菌株PD653中存在的一个基因组区域。在硅分析允许该区域内的三个开放阅读框被确定为参与HCB脱氯的候选基因。利用重组大肠杆菌细胞进行的实验表明，一个操纵子负责氧化HCB脱氯和五氯硝基苯脱硝。在大肠杆菌培养物中检测到代谢物五氯酚。在限氧条件下（[O2] < 0.5 mg l−1）的实验中，hcb降解活性明显低于好氧实验，这表明单加氧酶参与了反应。在这个操纵子中，hcba1被发现编码一个参与HCB脱氯的单加氧酶。该单加氧酶可能与hcba3编码的黄素还原酶形成复合物，提高PD653对hcb的降解活性。有机氯杀菌剂HCB广泛分布于环境中。生物修复技术可以有效地去除污染场所的六氯环己烷，但很少有研究分离到六氯环己烷降解微生物，并且尚未确定参与六氯环己烷降解的基因。在本研究中，鉴定了诺卡伊德菌株PD653矿化HCB初始阶段可能参与的基因。这些结果提高了我们对六氯甲烷脱氯生成五氯酚的蛋白质家族的认识。
Nocardioides sp. strain PD653 was the first identified aerobic bacterium capable of mineralizing hexachlorobenzene (HCB). In this study, strain PD653-B2, which was unexpectedly isolated from a subculture of strain PD653, was found to lack the ability to transform HCB or pentachloronitrobenzene into pentachlorophenol. Comparative genome analysis of the two strains revealed that genetic rearrangement had occurred in strain PD653-B2, with a genomic region present in strain PD653 being deleted.In silicoanalysis allowed three open reading frames within this region to be identified as candidate genes involved in HCB dechlorination. Assays using recombinant Escherichia coli cells revealed that an operon is responsible for both oxidative HCB dechlorination and pentachloronitrobenzene denitration. The metabolite pentachlorophenol was detected in the cultures produced in the E. coli assays. Significantly less HCB-degrading activity occurred in assays under oxygen-limited conditions ([O2] < 0.5 mg liter−1) than under aerobic assays, suggesting that monooxygenase is involved in the reaction. In this operon,hcbA1was found to encode a monooxygenase involved in HCB dechlorination. This monooxygenase may form a complex with the flavin reductase encoded byhcbA3, increasing the HCB-degrading activity of PD653.IMPORTANCEThe organochlorine fungicide HCB is widely distributed in the environment. Bioremediation can effectively remove HCB from contaminated sites, but HCB-degrading microorganisms have been isolated in few studies and the genes involved in HCB degradation have not been identified. In this study, possible genes involved in the initial step of the mineralization of HCB by Nocardioides sp. strain PD653 were identified. The results improve our understanding of the protein families involved in the dechlorination of HCB to give pentachlorophenol.