Burkholderia cenocepacia is a member of the Burkholderia cepacia complex (Bcc), a group of metabolically versatile bacteria that have emerged as opportunistic pathogens in cystic fibrosis and immunocompromised patients. Previously, a screen of transposon mutants in a rat pulmonary infection model identified an attenuated mutant with an insertion in paaE, a gene related to the phenylacetic acid (PA) catabolic pathway. In this study, we characterize gene clusters involved in the PA degradation pathway of B. cenocepacia K56-2 in relation to its pathogenicity in the Caenorhabditis elegans model of infection. We demonstrate that targeted-insertional mutagenesis of paaA and paaE, which encode part of the putative PA-coenzyme A ring-hydroxylation system, paaZ coding for a putative ring opening enzyme and paaF encoding part of the putative beta-oxidation system, severely reduce growth on PA as a sole carbon source. Insertional mutants in paaA and paaE were attenuated for virulence and expression of paaE in trans restored pathogenicity of the paaE mutant to wild type levels. Interruption of paaZ and paaF slightly increased virulence. Using gene interference by ingested double stranded (ds) RNA, we show that the attenuated phenotype of the paaA and paaE mutants is dependent on a functional
p38 mitogen-activated protein kinase pathway in C. elegans. Taken together, our results demonstrate that B. cenocepacia possesses a functional PA degradation pathway and that the putative PA-CoA ring-hydroxylation system is required for full pathogenicity in C. elegans.