Université de Strasbourg, UMR 7156 CNRS, Génétique Moléculaire, Génomique, Microbiologie, Strasbourg, France.
FEMS Microbiol Rev. 2020 Mar 1;44(2):189-207. doi: 10.1093/femsre/fuaa002.
Organohalides are organic molecules formed biotically and abiotically, both naturally and through industrial production. They are usually toxic and represent a health risk for living organisms, including humans. Bacteria capable of degrading organohalides for growth express dehalogenase genes encoding enzymes that cleave carbon-halogen bonds. Such bacteria are of potential high interest for bioremediation of contaminated sites. Dehalogenase genes are often part of gene clusters that may include regulators, accessory genes and genes for transporters and other enzymes of organohalide degradation pathways. Organohalides and their degradation products affect the activity of regulatory factors, and extensive genome-wide modulation of gene expression helps dehalogenating bacteria to cope with stresses associated with dehalogenation, such as intracellular increase of halides, dehalogenase-dependent acid production, organohalide toxicity and misrouting and bottlenecks in metabolic fluxes. This review focuses on transcriptional regulation of gene clusters for dehalogenation in bacteria, as studied in laboratory experiments and in situ. The diversity in gene content, organization and regulation of such gene clusters is highlighted for representative organohalide-degrading bacteria. Selected examples illustrate a key, overlooked role of regulatory processes, often strain-specific, for efficient dehalogenation and productive growth in presence of organohalides.
有机卤化物是在生物和非生物条件下形成的有机分子，包括自然形成和工业生产。它们通常具有毒性，对包括人类在内的生物体构成健康风险。能够为生长而降解有机卤化物的细菌表达脱卤酶基因，这些基因编码可裂解碳卤键的酶。此类细菌对于受污染场地的生物修复具有潜在的高度兴趣。脱卤酶基因通常是基因簇的一部分，这些基因簇可能包括调节剂、辅助基因以及用于转运和其他有机卤化物降解途径的酶的基因。有机卤化物及其降解产物会影响调节因子的活性，广泛的全基因组基因表达调控有助于脱卤细菌应对与脱卤相关的应激，例如卤化物在细胞内的增加、脱卤酶依赖性的产酸、有机卤化物毒性以及代谢通量的错误路由和瓶颈。本文综述了实验室实验和原位条件下细菌中脱卤基因簇的转录调控，突出了代表性的有机卤化物降解细菌中此类基因簇的基因内容、组织和调控多样性。选定的示例说明了通常是菌株特异性的调控过程在有效脱卤和在有机卤化物存在下进行生产性生长方面的关键但被忽视的作用。
