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Quorum sensing in Burkholderia cepacia: identification of the LuxRI homologs CepRI. - PubMed - NCBI

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J Bacteriol. 1999 Feb;181(3):748-56.

Quorum sensing in Burkholderia cepacia: identification of the LuxRI homologs CepRI.

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


Burkholderia cepacia has emerged as an important pathogen in patients with cystic fibrosis. Many gram-negative pathogens regulate the production of extracellular virulence factors by a cell density-dependent mechanism termed quorum sensing, which involves production of diffusible N-acylated homoserine lactone signal molecules, called autoinducers. Transposon insertion mutants of B. cepacia K56-2 which hyperproduced siderophores on chrome azurol S agar were identified. One mutant, K56-R2, contained an insertion in a luxR homolog that was designated cepR. The flanking DNA region was used to clone the wild-type copy of cepR. Sequence analysis revealed the presence of cepI, a luxI homolog, located 727 bp upstream and divergently transcribed from cepR. A lux box-like sequence was identified upstream of cepI. CepR was 36% identical to Pseudomonas aeruginosa RhlR and 67% identical to SolR of Ralstonia solanacearum. CepI was 38% identical to RhlI and 64% identical to SolI. K56-R2 demonstrated a 67% increase in the production of the siderophore ornibactin, was protease negative on dialyzed brain heart infusion milk agar, and produced 45% less lipase activity in comparison to the parental strain. Complementation of a cepR mutation restored parental levels of ornibactin and protease but not lipase. An N-acylhomoserine lactone was purified from culture fluids and identified as N-octanoylhomoserine lactone. K56-I2, a cepI mutant, was created and shown not to produce N-octanoylhomoserine lactone. K56-I2 hyperproduced ornibactin and did not produce protease. These data suggest both a positive and negative role for cepIR in the regulation of extracellular virulence factor production by B. cepacia.

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