Intraspecies Signaling Involving the Diffusible Signal Factor BDSF (cis-2-Dodecenoic Acid) Influences Virulence inBurkholderia cenocepacia

Abstract

Burkholderia cenocepacia produces a diffusible fatty acid signal molecule, cis-2-dodecenoic acid (BDSF), that has been implicated in interspecies and interkingdom communication. Here, we show that BDSF also acts as an intraspecies signal in B. cenocepacia to control factors contributing to virulence of this major opportunistic pathogen.Many bacteria use cell-cell communication systems involving the synthesis and perception of diffusible signal molecules to monitor aspects of their environment such as cell density or confinement to niches and to modulate their behavior accordingly (reviewed in references 3, 7, 16, 26, and 27). The signal molecules produced by bacteria are structurally diverse. Many gram-negative bacteria use N-acyl homoserine lactones (NAHLs) as signals, although other fatty acid derivatives, including cis-unsaturated fatty acids, are also found. The first example of this latter class of molecule to be described was the diffusible signal factor DSF from the plant pathogen Xanthomonas campestris pv. campestris, which is cis-11-methyl-2-dodecenoic acid (1, 25). Until recently, it was thought that signal molecules of the DSF family were restricted to the xanthomonads, which do not synthesize N-AHLs (4, 11). However, work by Boon and colleagues (2) has demonstrated that Burkholderia cenocepacia, the opportunistic pathogen of cystic fibrosis patients and immunocompromised individuals, produces the DSF-like molecule cis-2-dodecenoic acid (BDSF). This molecule is able to activate DSF-dependent responses in X. campestris pv. campestris and to inhibit germ tube formation in Candida albicans, suggesting a role in interspecies and interkingdom communication. B. cenocepacia produces N-AHLs to regulate a wide range of functions that include virulence, biofilm formation, and motility (9, 23). This raises the question as to whether BDSF has any role as an intraspecies signal in B. cenocepacia J2315, an issue that we address here.BDSF synthesis requires BCAM0581, which is related to the DSF synthase RpfF of X. campestris pv. campestris (1, 2). We have examined the role of BDSF in signaling by comparing the phenotypes of wild-type B. cenocepacia J2315, an rpfF mutant with a deletion in bcam0581, and a complemented mutant strain (Table 1). A strain carrying an in-frame deletion of rpfF was constructed by allelic exchange. DNA fragments comprising the upstream and downstream regions flanking rpfF in the genome were amplified by PCR, using B. cenocepacia genomic DNA as a template and the primer sets RPFFUF/RPFFUR and RPFFDF/ RPFFDR, respectively (Table 1). The amplicons were mixed, diluted, and used as a template for PCR with RPFFUF and RPFFDR as the primers. To facilitate construction, restriction sites for BamHI and HindIII were engineered into these primer sequences. The amplified DNA fragment was cut with BamHI and HindIII and ligated into the allelic exchange vector pEX18Tc to give pEXRPFF. The construction was verified by DNA sequencing. The construct was introduced into B. cenocepacia J2315 by electroporation...

Differential Modulation ofBurkholderia cenocepaciaVirulence and Energy Metabolism by the Quorum-Sensing Signal BDSF and Its Synthase

“…Likewise, expression of the virulence regulon in Xanthomonas campestris is coregulated by the QS signal DSF and hypoxia cue (11). Interestingly, a recent study suggested that BDSF regulates virulence gene expression in B. cenocepacia independent of the AHL-type QS system (32). Given that the BDSF-dependent genes identified in that study are different from the virulence genes characterized this paper, it is a possibility that in addition to coregulation of a common set of virulence genes, BDSF and AHL may also have their own separate regulons.…”

A Decade of Burkholderia cenocepacia Virulence Determinant Research

“…B. cenocepacia has one such system and produces cis-2-dodecenoic acid in a cell density-dependent manner (19). This diffusible signal molecule alters many of the same functions controlled by cepRI, cciRI, and cepR2; mutants unable to synthesize cis-2-dodecenoic acid have decreased motility, biofilm synthesis, and virulence in the G. mellonella moth larvae and zebra fish infection models (19,44,136). This molecule may also be involved in communication between B. cenocepacia and other (19).…”

Structural and Functional Characterization of Diffusible Signal Factor Family Quorum-Sensing Signals Produced by Members of the Burkholderia cepacia Complex

“…More recently, another QS signal molecule, cis-2-dodecenoic acid (BDSF), has been identified in B. cenocepacia (3). Subsequent studies showed that BDSF plays a role in the regulation of bacterial virulence (6,20). Interestingly, the two QS systems appear to act in conjunction in the regulation of B. cenocepacia virulence, as a set of the AHL-controlled virulence genes are also positively regulated by BDSF (6).…”