Hellberg Lindqvist Miriam, Nilsson Thomas, Sundin Pontus, Rova Maria
Department of Engineering and Chemical Sciences, Karlstad University, SE 651 88 Karlstad, Sweden.
Department of Engineering and Chemical Sciences, Karlstad University, SE 651 88 Karlstad, Sweden
FEMS Microbiol Lett. 2015 Mar;362(6). doi: 10.1093/femsle/fnv019. Epub 2015 Feb 11.
The chlorate-respiring bacterium Ideonella dechloratans is a facultative anaerobe that can use both oxygen and chlorate as terminal electron acceptors. The genes for the enzymes chlorate reductase (clrABDC) and chlorite dismutase, necessary for chlorate metabolism and probably acquired by lateral gene transfer, are located in a gene cluster that also includes other genes potentially important for chlorate metabolism. Among those are a gene for cytochrome c (cyc) whose gene product may serve as an electron carrier during chlorate reduction, a cofactor biosynthesis gene (mobB) and a predicted transcriptional regulator (arsR). Only chlorate reductase and chlorite dismutase have been shown to be expressed in vivo. Here, we report the in vivo production of a single polycistronic transcript covering eight open reading frames including clrABDC, cyc, mobB and arsR. Transcription levels of the cyc and clrA genes were compared to each other by the use of qRT-PCR in RNA preparations from cells grown under aerobic or chlorate reducing anaerobic conditions. The two genes showed the same mRNA levels under both growth regimes, indicating that no transcription termination occurs between them. Higher transcription levels were observed at growth without external oxygen supply. Implications for electron pathway integration following lateral gene transfer are discussed.
能利用氯酸盐呼吸的细菌脱氯伊代奥菌是一种兼性厌氧菌，它既可以利用氧气也可以利用氯酸盐作为末端电子受体。氯酸盐代谢所必需的氯酸还原酶（clrABDC）和亚氯酸盐歧化酶的基因可能是通过横向基因转移获得的，它们位于一个基因簇中，该基因簇还包括其他可能对氯酸盐代谢很重要的基因。其中有一个细胞色素c（cyc）基因，其基因产物可能在氯酸盐还原过程中作为电子载体，一个辅因子生物合成基因（mobB）和一个预测的转录调节因子（arsR）。只有氯酸还原酶和亚氯酸盐歧化酶已被证明在体内表达。在此，我们报告了一种单一多顺反子转录本在体内的产生，该转录本涵盖了八个开放阅读框，包括clrABDC、cyc、mobB和arsR。通过使用qRT-PCR在有氧或在氯酸盐还原厌氧条件下生长的细胞的RNA制剂中比较cyc和clrA基因的转录水平。在两种生长条件下，这两个基因显示出相同的mRNA水平，表明它们之间没有发生转录终止。在没有外部氧气供应的生长条件下观察到更高的转录水平。讨论了横向基因转移后对电子途径整合的影响。
