Transcriptional regulation of the acetyl-CoA synthetase gene acsA in Pseudomonas aeruginosa
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S H O R T CO M MU N I C A T I O N
Transcriptional regulation of the acetyl-CoA synthetase gene acsA in Pseudomonas aeruginosa Utta Kretzschmar · Viola Khodaverdi · Lorenz Adrian
Received: 10 March 2010 / Revised: 25 May 2010 / Accepted: 27 May 2010 / Published online: 15 June 2010 © Springer-Verlag 2010
Abstract Pseudomonas aeruginosa ATCC 17933 is able to oxidize ethanol to acetate under aerobic conditions. The P. aeruginosa acetyl-CoA synthetase (ACS) gene acsA was previously identiWed, and the ACS enzyme described to be required for growth on ethanol as the sole source of carbon and energy. Here, we investigated the transcriptional regulation of the acsA gene using an acsA::lacZ fusion. Transcription of acsA was regulated by the carbon source, and expression was maximal on ethanol, acetate and propionate. In addition, the induction depended on the response regulator ErdR, which also regulates hierarchically arranged genes for ethanol oxidation. Transcription of the acsA gene was repressed by addition of succinate to an ethanol-containing medium. This repression required Crc, the product of the catabolite repression control gene crc. Keywords Acetyl-CoA synthetase · Catabolite repression · Ethanol oxidation · Pseudomonas aeruginosa · Transcriptional regulation Abbreviations ACS Acetyl-CoA synthetase crc Catabolite repression control ACK Acetate kinase PTA Phosphotransacetylase Communicated by Timothy Donohue. U. Kretzschmar · V. Khodaverdi · L. Adrian Fachgebiet Angewandte Biochemie, Institut für Biotechnologie, Technische Universität Berlin, Seestraße 13, 13353 Berlin, Germany L. Adrian (&) Helmholtzzentrum für Umweltforschung (UFZ), Permoser Straße 15, 04318 Leipzig, Germany e-mail: [email protected]
Introduction Upon aerobic growth on ethanol as the sole source of carbon and energy, Pseudomonas aeruginosa ATCC 17933 induces a pyrroloquinoline quinone (PQQ)-dependent ethanol oxidation system. It consists of an ethanol dehydrogenase with PQQ as prosthetic group (QEDH) (Rupp and Görisch 1988) encoded by the exaA gene, a soluble cytochrome c550 encoded by exaB and the pqqABCDE gene cluster that encodes proteins for PQQ biosynthesis (Schobert and Görisch 1999). A NAD-dependent acetaldehyde dehydrogenase (exaC) oxidizes acetaldehyde to acetate (Schobert and Görisch 1999). Regulatory genes were identiWed that control the ethanol-oxidizing system in a hierarchical manner (Görisch 2003). Transcription from the exaA promoter is controlled by the two-component system ExaDE (Fig. 1). The gene exaD encodes a histidine sensor kinase and exaE a response regulator (Schobert and Görisch 2001). A further response regulator, AgmR, controls transcription of the two-component system ExaDE and the exaB and pqq operons (Gliese et al. 2004). The response regulator ErdR directs transcription of agmR and was proposed to also control acetate metabolism (Görisch 2003). Pseudomonas aeruginosa can also grow with acetate as the sole source of carbon and energy under aerobic conditions. Acetate is converted to acetyl-CoA and successivel
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