FUNCTIONAL CHARACTERIZATION OF TWO PHENYLACETYL-COA LIGASES IN BURKHOLDERIA CENOCEPACIA
Burkholderia cenocepacia causes Cepacia syndrome, a fatal pneumonia that affects Cystic Fibrosis patients. Aromatic degradation has been linked to virulence in B. cenocepacia by insertional mutagenesis of genes involved in phenylacetic acid catabolism. B. cenocepacia has two paralogous copies of PaaK, the phenylacetyl-CoA ligase, which produces PA-CoA, the inducer of the pathway. Our objective was to assess a role for PaaK1 and PaaK2 in PA metabolism and virulence by constructing clean deletion mutants for each gene, and a double paaK mutant, as well as to quantify virulence using the nematode host model. Deletion and complementation of paaK1 revealed no change in killing phenotype. Reporter activity assays revealed PaaK1-dependent induction of the PA pathway 3-hydroxyphenylacetic acid but not 4-hydroxyphenylacetic acid. Altogether, these results demonstrate that 3-OHPA induces the PA degradation pathway in a paaK1 dependent manner and that PaaK1 is not involved in pathogenicity.