Expression of the bviIR and cepIR Quorum-Sensing Systems of Burkholderia vietnamiensis

Department of Microbiology and Infectious Diseases, University of Calgary Health Sciences Center, Calgary, Alberta, Canada T2N 4N1

^* To whom correspondence should be addressed. Email: psokol{at}ucalgary.ca.

	Abstract

Burkholderia vietnamiensis has both the cepIR quorum-sensing system that is widely distributed among the Burkholderia cepacia complex (Bcc) and the bviIR system. Comparison of the expression of cepI, cepR, bviI and bviR-luxCDABE fusions in B. vietnamiensis G4 and G4 cepR and bviR mutants determined that the expression of bviI requires both a functional cognate regulator, BviR and functional CepR. The cepIR system, however, is not regulated by BviR. Unlike the cepIR genes in other Bcc species, the cepIR genes are not auto-regulated in G4. AHL production profiles in G4 cepI, cepR, bviI and bviR mutants confirmed the regulatory organization of the G4 quorum-sensing systems. The regulatory network in strain PC259 is similar to G4, except the CepR positively regulates cepI and negatively regulates cepR. AHL production and bviI expression in seven B. vietnamiensis isolates were compared. All strains produced N-octanoyl-homoserine lactone (OHL) and N-hexanoyl-homoserine lactone (HHL); however, only one of four clinical strains but all three environmental strains produced the BviI synthase product, N-decanoyl-homoserine lactone (DHL). The three strains that did not produce DHL expressed bviR but not bviI. Heterologous expression of bviR restored DHL production in these strains. The bviIR loci of the non-DHL producing strains were sequenced to confirm that bviR encodes for a functional transcriptional regulator. Lack of expression of bviI_G4 in these three strains indicated that an additional regulatory element may be involved in the regulation of bviIR expression in certain strains of B. vietnamiensis.