Inactivation of cytochrome o ubiquinol oxidase relieves catabolic repression of the Pseudomonas putida GPo1 alkane degradation pathway
Inactivation of cytochrome o ubiquinol oxidase relieves catabolic repression of the Pseudomonas putida GPo1 alkane degradation pathway
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DOI：
10.1128/jb.184.14.3785-3793.2002
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发表时间：
2002-07-01
影响因子：
3.2
通讯作者：
Rojo, F
中科院分区：
文献类型：
--
作者：
Dinamarca, MA;Ruiz-Manzano, A;Rojo, F
恶臭假单胞菌GPo 1的OCT质粒编码的烷烃降解途径的表达受两个控制系统调节。一种依赖于转录调节因子AlkS，其在烷烃存在下激活途径的表达。另一个是占主导地位的全局调节控制，当生长培养基中除了烷烃之外还存在优选的碳源时，抑制途径基因的表达。这种分解代谢产物抑制控制通过一种表征不佳的机制发生，该机制最终调节来自该途径的两个AMS激活的启动子的转录。为了确定所涉及的因素，开发了一种筛选方法来分离没有这种控制的突变体。获得了几个菌株，所有这些菌株都含有映射到编码细胞色素o泛醇氧化酶的基因的突变，该氧化酶是在高度需氧条件下电子传递链的主要末端氧化酶。消除这一终端氧化酶导致减少在丰富的Luria-Bertani培养基中观察到的分解代谢抑制，并在含有乳酸盐或琥珀酸盐作为碳源的限定培养基。这表明，分解代谢阻遏可以通过使用来自细胞的电子传递链或氧化还原状态的信息来监测生理或代谢状态。由于crc基因的失活也减少了丰富培养基中的分解代谢抑制（尽管在成分确定的培养基中没有观察到），因此产生了既缺乏Crc功能又缺乏细胞色素o末端氧化酶的菌株。这两个突变在丰富培养基中具有解除分解代谢阻遏的累加效应。这表明crc和cyo属于不同的调节途径，都参与了分解代谢抑制。
Expression of the alkane degradation pathway encoded by the OCT plasmid of Pseudomonas putida GPo1 is regulated by two control systems. One relies on the transcriptional regulator AlkS, which activates expression of the pathway in the presence of alkanes. The other, which is a dominant global regulation control, represses the expression of the pathway genes when a preferred carbon source is present in the growth medium in addition to alkanes. This catabolite repression control occurs through a poorly characterized mechanism that ultimately regulates transcription from the two AMS-activated promoters of the pathway. To identify the factors involved, a screening method was developed to isolate mutants without this control. Several isolates were obtained, all of which contained mutations that mapped to genes encoding cytochrome o ubiquinol oxidase, the main terminal oxidase of the electron transport chain under highly aerobic conditions. Elimination of this terminal oxidase led to a decrease in the catabolic repression observed both in rich Luria-Bertani medium and in a defined medium containing lactate or succinate as the carbon source. This suggests that catabolic repression could monitor the physiological or metabolic status by using information from the electron transport chain or from the redox state of the cell. Since inactivation of the crc gene also reduces catabolic repression in rich medium (although not that observed in a defined medium), a strain was generated lacking both the Crc function and the cytochrome o terminal oxidase. The two mutations had an additive effect in relieving catabolic repression in rich medium. This suggests that crc and cyo belong to different regulation pathways, both contributing to catabolic repression.