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Journal of Bacteriology, August 2008, p. 5339-5352, Vol. 190, No. 15
0021-9193/08/$08.00+0     doi:10.1128/JB.00400-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Burkholderia pseudomallei, B. thailandensis, and B. ambifaria Produce 4-Hydroxy-2-Alkylquinoline Analogues with a Methyl Group at the 3 Position That Is Required for Quorum-Sensing Regulation

INRS-Institut Armand Frappier, 531 Boulevard des Prairies, Laval, Québec H7V 1B7, Canada,¹ Department of Microbiology and Infectious Diseases, Faculty of Medicine, University of Calgary Health Sciences Centre, 3330 Hospital Drive, NW, Calgary, Alberta T2N 4N1, Canada²

Received 20 March 2008/ Accepted 14 May 2008

4-Hydroxy-2-alkylquinolines (HAQs), especially 3,4-dihydroxy-2-heptylquinoline (Pseudomonas quinolone signal) and its precursor, 4-hydroxy-2-heptylquinoline, are attracting much attention, mainly because of their role as signaling molecules in Pseudomonas aeruginosa. The pqsABCDE operon is centrally involved in their biosynthesis. The presence of a homologous operon in Burkholderia pseudomallei and B. thailandensis was recently reported. Thus, we have investigated the abilities of 11 Burkholderia species to produce HAQ-like molecules by liquid chromatography/mass spectrometry. We have identified 29 different HAQ derivatives produced by the only three Burkholderia species where a pqsABCDE homologue was found among available sequenced Burkholderia species genomes, including B. ambifaria, a member of the Burkholderia cepacia complex. In contrast with those of P. aeruginosa, Burkholderia HAQs typically bear a methyl group, hence their designation as 4-hydroxy-3-methyl-2-alkylquinolines (HMAQs). We identified three families of HMAQs with a saturated or unsaturated alkyl chain at the 2' position, in contrast with the 1' position of P. aeruginosa, including one with an N-oxide group. Furthermore, the operon in these species contains two more genes downstream of the pqsE homologue, resulting in the hmqABCDEFG operon. While the inactivation of hmqA inhibits the production of HMAQs, the methylation of the quinoline ring requires a putative methyltransferase encoded by hmqG. Interestingly, hmqA or hmqG mutations increase the production of acyl homoserine lactones and, consequently, phenotypes under the control of quorum sensing in B. ambifaria: antifungal activity, siderophore production, and proteolytic activity. These results indicate that only HAQs bearing a methyl group (HMAQs) are involved in quorum-sensing regulation.

Published ahead of print on 6 June 2008.