Identification of a Novel Virulence Factor in Burkholderia cenocepacia H111 Required for Efficient Slow Killing of Caenorhabditis elegans

Abstract

Burkholderia cenocepacia H111, which was isolated from a cystic fibrosis patient, employs a quorum-sensing (QS) system, encoded by cep, to control the expression of virulence factors as well as the formation of biofilms. The QS system is thought to ensure that pathogenic traits are expressed only when the bacterial population density is high enough to overwhelm the host before it is able to mount an efficient response. While the wild-type strain effectively kills the nematode Caenorhabditis elegans, the pathogenicity of mutants with defective quorum sensing is attenuated. To date, very little is known about the cep-regulated virulence factors required for nematode killing. Here we report the identification of a cep-regulated gene, whose predicted amino acid sequence is highly similar to the QS-regulated protein AidA of the plant pathogen Ralstonia solanacearum. By use of polyclonal antibodies directed against AidA, it is demonstrated that the protein is expressed in the late-exponential phase and accumulates during growth arrest. We show that B. cenocepacia H111 AidA is essential for slow killing of C. elegans but has little effect on fast killing, suggesting that the protein plays a role in the accumulation of the strain in the nematode gut. Thus, AidA appears to be required for establishing an infection-like process rather than acting as a toxin. Furthermore, evidence is provided that AidA is produced not only by B. cenocepacia but also by many other strains of the Burkholderia cepacia complex.

A Burkholderia cenocepacia Orphan LuxR Homolog Is Involved in Quorum-Sensing Regulation

“…cenocepacia virulence against the nematode Caenorhabditis elegans is positively influenced by AidA protein production (34). The increase in aidA expression in K56-2cepR2b compared to K56-2 observed by microarray analysis was independently confirmed by qRT-PCR ( Table 2).…”

The Type 2 Secretion Pseudopilin, gspJ , Is Required for Multihost Pathogenicity of Burkholderia cenocepacia AU1054

“…However, the mechanisms of fast killing by AU1054 are not fully understood. Quorum sensing and the quorumsensing regulated protein AidA are known to be required for B. cenocepacia H111, an ET12 epidemic clonal strain, to infect and kill C. elegans on slow kill media (35,41). Mutants defective in quorum sensing or Aid were not obtained in the present study, although we also expect them to be important for AU1054 virulence.…”

Identification of Specific and Universal Virulence Factors in Burkholderia cenocepacia Strains by Using Multiple Infection Hosts

“…For Western blotting, whole-cell proteins were separated in a 15% sodium dodecyl sulfate-polyacrylamide gel and transferred to a polyvinylidene difluoride membrane (Immobilon-P; Millipore, Eschborn, Germany). The membrane was probed with anti-AidA antibodies (27), and detection reactions were performed with alkaline phosphatase-conjugated anti-rabbit immunoglobulin G (Sigma, Steinheim, Germany) according to the recommendations of the manufacturer (Roche, Mannheim, Germany).…”