The PQQ biosynthetic operons and their transcriptional regulation in Pseudomonas aeruginosa
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ORIGINAL PAPER
The PQQ biosynthetic operons and their transcriptional regulation in Pseudomonas aeruginosa Nicole Gliese • Viola Khodaverdi • Helmut Go¨risch
Received: 12 August 2009 / Revised: 14 October 2009 / Accepted: 21 October 2009 / Published online: 10 November 2009 Ó Springer-Verlag 2009
Abstract Gene PA1990 of Pseudomonas aeruginosa, located downstream of pqqE and encoding a putative peptidase, was shown to be involved in excretion of PQQ into the culture supernatant. This gene is cotranscribed with the pqqABCDE cluster and was named pqqH. A PA1990::Kmr mutant (VK3) did not show any effect in growth behaviour; however, in contrast to the wild-type, no excretion of PQQ into the culture supernatant was observed. The putative pqqF gene of P. aeruginosa was shown to be essential for PQQ biosynthesis. A pqqF::Kmr mutant did not grow aerobically on ethanol, because of its inability to produce PQQ. Transcription of the pqqABCDEH operon was induced upon aerobic growth on ethanol, 1-propanol, 1,2-propanediol and 1-butanol, while on glycerol, succinate and acetate, transcription was low. Transcription of the pqqABCDEH operon was also found upon anoxic growth on ethanol with nitrate as electron acceptor, but no PQQ was produced. Expression of the pqqABCDEH operon is regulated at the transcriptional level. In contrast, the pqqF operon appeared to be transcribed constitutively at a very low level under all growth conditions studied.
Communicated by Arnold Driessen. N. Gliese BioGenes GmbH, Koepenicker Strasse 325, 12555 Berlin, Germany V. Khodaverdi H. Go¨risch (&) Fachgebiet Angewandte Biochemie, Institut fu¨r Biotechnologie, Technische Universita¨t Berlin, Seestraße 13, 13353 Berlin, Germany e-mail: [email protected]
Keywords Pseudomonas aeruginosa Ethanol oxidation Transcriptional regulation pqqABCDEH pqqF Abbreviations cyt. c550 Cytochrome c550 Km Kanamycin PQQ Pyrroloquinoline quinone QEDH Quinoprotein ethanol dehydrogenase WT Wild-type
Introduction Pseudomonas aeruginosa ATCC 17933 grows aerobically on ethanol using a periplasmic quinoprotein ethanol dehydrogenase (QEDH) that contains pyrroloquinoline quinone (PQQ) as cofactor (Rupp and Go¨risch 1988). The QEDH transfers electrons to a terminal oxidase via a soluble cytochrome c550 (Reichmann and Go¨risch 1993). Transcriptional regulation of the exaA gene encoding QEDH, the exaBC operon encoding cytochrome c550 and a NAD?-dependent acetaldehyde dehydrogenase had been studied previously on different carbon sources (Schobert and Go¨risch 2001). The regulation of the PQQ biosynthetic genes of P. aeruginosa is still unknown. Previously, we showed that gene erbR (former agmR) and further two component regulatory systems are involved not only in the regulation of transcription of the putative pqqABCDE operon but also of the operons exaA and exaBC of P. aeruginosa (Gliese et al. 2004, Mern et al. 2009). Number and organization of PQQ biosynthetic genes differ from organism to organism. In P. aeruginosa, PQQ
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