Many bacteria metabolize aromatic compounds via catechol as a catabolic intermediate, and possess multiple genes or clusters encoding catechol-cleavage enzymes. The presence of multiple isozyme-encoding genes is a widespread phenomenon that seems to give the carrying strains a selective advantage in the natural environment over those with only a single copy. In the naphthalene-degrading strain Pseudomonas putida ND6, catechol can be converted into intermediates of the tricarboxylic acid cycle via either ortho- or meta-cleavage pathway. In this study, we demonstrated that the catechol ortho-cleavage pathway genes (catB_ICIAI and catB_IIC_IIA_II) on the chromosome play an important role. The cat_I and cat_II operons are co-transcribed, whereas catAI and catAII are under independent transcriptional regulation. We examined the binding of regulatory proteins to promoters. Inthe presence of cis-cis-muconate, a well-studied inducer of the cat gene cluster, CatR_I and CatR_II occupy an additional downstream site, designated as the activation binding site. Notably, CatR_I binds to both the cat_I and cat_II promoters with high affinity, while CatR_II binds weakly. This is likely caused by a T to G mutation in the G/T-N₁₁-A motif. Specifically, we found that CatR_I and CatR_II regulate catB_IC_IA_I and catB_IIC_IIA_II in a cooperative manner, which provides new insights into naphthalene degradation.

中文翻译：

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恶臭假单胞菌 ND6 中两个儿茶酚降解基因簇的功能和分子生态学意义。

许多细菌通过儿茶酚作为分解代谢中间体代谢芳香族化合物，并拥有编码儿茶酚裂解酶的多个基因或簇。多个同工酶编码基因的存在是一种普遍现象，与只有一个拷贝的菌株相比，携带菌株似乎在自然环境中具有选择性优势。在萘降解菌株Pseudomonas putida ND6 中，儿茶酚可以通过邻位或间位裂解途径转化为三羧酸循环的中间体。在这项研究中，我们证明了儿茶酚邻位裂解途径基因 ( catB _{I C I A I}和catB _IIC _II A _II )对染色体起着重要的作用。cat _I和cat _II操纵子是共转录的，而 catAI 和 catAII 处于独立的转录调控之下。我们检查了调节蛋白与启动子的结合。在顺式-顺式-粘康酸盐（一种经过充分研究的 cat 基因簇诱导剂）存在的情况下，CatR _I和 CatR _II占据了一个额外的下游位点，指定为激活结合位点。值得注意的是，CatR _I以高亲和力结合cat _I和cat _II启动子，而 CatR _II弱结合。_{这可能是由 G/TN 11} -A 基序中的 T 到 G 突变引起的。具体来说，我们发现 CatR _I和 CatR _II以合作的方式调节catB _I C _I A _I和catB _II C _II A _II，这为萘降解提供了新的见解。