Transcriptional Regulation of the Peripheral Pathway for the Anaerobic Catabolism of Toluene and m-Xylene in Azoarcus sp. CIB.
Transcriptional Regulation of the Peripheral Pathway for the Anaerobic Catabolism of Toluene and m-Xylene in Azoarcus sp. CIB.
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DOI：
10.3389/fmicb.2018.00506
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发表时间：
2018
影响因子：
5.2
通讯作者：
Díaz E
中科院分区：
文献类型：
--
作者：
Blázquez B;Carmona M;Díaz E
烷基苯，例如甲苯和间二甲苯，是一类重要的碳氢化合物污染物，它们分布广泛，并且往往在地下缺氧环境中积聚。细菌中甲苯厌氧氧化的外周途径包括由苄基琥珀酸合酶（由 bss 基因编码）催化的初始激活，以及随后将苄基琥珀酸β-氧化为苯甲酰辅酶 A 和琥珀酰辅酶 A（由 bbs 基因编码）。我们在此表明，位于整合和共轭元件内的 bss 和 bbs 基因对于甲苯的厌氧降解至关重要，而且对于反硝化 β-变形菌 Azoarcus sp 中的间二甲苯氧化也至关重要。 CIB。提出了对单个细菌菌株中甲苯/间二甲苯厌氧分解代谢的完整基因簇的转录组织和调节的新见解。 bss 和 bbs 基因转录耦合成两个大的聚合分解代谢操纵子，分别由 PbssD 和 PbbsA 启动子驱动，当细胞在甲苯或间二甲苯中厌氧生长时，其表达是可诱导的。由 PtdiS 启动子驱动的相邻 tdiSR 操纵子编码一个假定的双组分调控系统。 TdiR 充当 PbssD、PbbsA 和 PtdiS 启动子的转录激活剂，是琥珀酸苄酯/(3-甲基)苄基琥珀酸，而不是甲苯/间二甲苯，后者是可能触发 TdiS 介导的 TdiR 激活的诱导剂。除了基于 TdiSR 的特异性控制外，Azoarcus sp 中 bss 和 bbs 基因的表达。 CIB 受到过度监管，该监管取决于某些环境因素，例如氧气的存在/不存在或首选碳源的可用性（分解代谢物抑制）。这项工作为未来可靠评估甲苯/间二甲苯污染环境中微生物活动的策略铺平了道路。
Alkylbenzenes, such as toluene and m-xylene, are an important class of contaminant hydrocarbons that are widespread and tend to accumulate in subsurface anoxic environments. The peripheral pathway for the anaerobic oxidation of toluene in bacteria consists of an initial activation catalyzed by a benzylsuccinate synthase (encoded by bss genes), and a subsequent modified β-oxidation of benzylsuccinate to benzoyl-CoA and succinyl-CoA (encoded by bbs genes). We have shown here that the bss and bbs genes, which are located within an integrative and conjugative element, are essential for anaerobic degradation of toluene but also for m-xylene oxidation in the denitrifying beta-proteobacterium Azoarcus sp. CIB. New insights into the transcriptional organization and regulation of a complete gene cluster for anaerobic catabolism of toluene/m-xylene in a single bacterial strain are presented. The bss and bbs genes are transcriptionally coupled into two large convergent catabolic operons driven by the PbssD and PbbsA promoters, respectively, whose expression is inducible when cells grow anaerobically in toluene or m-xylene. An adjacent tdiSR operon driven by the PtdiS promoter encodes a putative two-component regulatory system. TdiR behaves as a transcriptional activator of the PbssD, PbbsA, and PtdiS promoters, being benzylsuccinate/(3-methyl)benzylsuccinate, rather than toluene/m-xylene, the inducers that may trigger the TdiS-mediated activation of TdiR. In addition to the TdiSR-based specific control, the expression of the bss and bbs genes in Azoarcus sp. CIB is under an overimposed regulation that depends on certain environmental factors, such as the presence/absence of oxygen or the availability of preferred carbon sources (catabolite repression). This work paves the way for future strategies toward the reliable assessment of microbial activity in toluene/m-xylene contaminated environments.
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影响因子：
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