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.

中文翻译：

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细菌中有机卤化物污染物利用的转录调控。

有机卤化物是天然和通过工业生产生物和非生物形式形成的有机分子。它们通常是有毒的，对包括人类在内的活生物体均构成健康风险。能够降解有机卤化物以使其生长的细菌表达脱卤酶基因，该基因编码裂解碳-卤键的酶。这种细菌对于污染部位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，可能包括调节剂，辅助基因以及转运蛋白和有机卤化物降解途径的其他酶的基因。有机卤化物及其降解产物会影响调节因子的活性，广泛的全基因表达调控可帮助细菌脱卤，以应对与脱卤相关的压力，例如细胞内卤化物的增加，脱卤酶依赖性酸的产生，有机卤化物的毒性以及代谢通量的误导和瓶颈。这篇综述着重于细菌脱卤基因簇的转录调控，如实验室实验和原位。对于代表性的降解有机卤化物的细菌，强调了这种基因簇的基因含量，组织和调控的多样性。选定的例子说明了在有机卤化物存在下有效进行脱卤和生产性生长的调节过程（通常是菌株特异性的）的关键而被忽略的作用。