Polybrominated diphenyl ethers (PBDEs), chemicals commonly used as flame-retardants in consumer products, are emerging persistent organic pollutants that are ubiquitous in the environment. In this study, we report a PBDE-respiring isolate - Dehalococcoides mccartyi strain GY50, which debrominates the most toxic tetra- and penta-BDE congeners (∼1.4 µM) to diphenyl ether within 12 days with hydrogen as the electron donor. The complete genome sequence revealed 26 reductive dehalogenase homologous genes (rdhAs), among which three genes (pbrA1, pbrA2 and pbrA3) were highly expressed during PBDE debromination. After 10 transfers of GY50 with trichloroethene or 2,4,6-trichlorophenol as the electron acceptor instead of PBDEs, the ssrA-specific genome island (ssrA-GI) containing pbrA1 and pbrA2 was deleted from the genome of strain GY50, leading to two variants (strain GY52 with trichloroethene, strain GY55 with 2,4,6-trichlorophenol) with identically impaired debromination capabilities (debromination of penta-/tetra-BDEs ceased at di-BDE 15). Through analysis of Illumina paired-end sequencing data, we identified read pairs that probably came from variants that contain ssrA-GI deletions, indicating their possible presence in the original strain GY50 culture. The two variant strains provide real-time examples on rapid evolution of organohalide-respiring organisms. As PBDE-respiring organisms, GY50-like strains may serve as key players in detoxifying PBDEs in contaminated environments.

译文

多溴联苯醚 (PBDEs) 是消费品中常用作阻燃剂的化学品,是环境中普遍存在的新兴持久性有机污染物。在这项研究中,我们报告了一个PBDE呼吸分离物-Dehalococcoides mccartyi菌株GY50,该菌株在12天内以氢为电子供体将毒性最大的四溴化和五溴化同系物 (〜1.4 µ m) 脱溴为二苯醚。完整的基因组序列揭示了26个还原脱卤酶同源基因 (rdha),其中三个基因 (pbrA1,pbrA2和pbrA3) 在PBDE脱溴过程中高度表达。用三氯乙烯或2,4,6-三氯苯酚作为电子受体而不是多溴二苯醚对GY50进行10次转移后,从菌株GY50的基因组中删除了含有pbrA1和pbrA2的ssrA特异性基因组岛 (ssrA-GI),导致两个变体 (具有三氯乙烯的菌株GY52,具有2,4的菌株GY55,6-三氯苯酚) 的脱溴能力同样受损 (五溴/四溴二苯醚的脱溴在二溴二苯醚15时停止)。通过对Illumina配对末端测序数据的分析,我们确定了可能来自包含ssrA-GI缺失的变体的读取对,表明它们可能存在于原始菌株GY50培养物中。这两个变体菌株提供了有关有机卤化物呼吸生物快速进化的实时示例。作为多溴二苯醚呼吸的生物,GY50-like菌株可能是污染环境中多溴二苯醚解毒的关键角色。

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