Taxonomic studies have shown that Burkholderia cenocepacia is a member of the Burkholderia cepacia complex (Bcc), a group of at least 17 distinct, but closely related species. Strains of the Bcc are ubiquitously distributed in nature and have been isolated from soil, water, the rhizosphere of plants, industrial settings, hospital environments, and from infected humans. Bcc strains have an enormous biotechnological potential and have been used for bioremediation of recalcitrant xenobiotics, plant growth promotion, and biocontrol purposes. At the same time, however, Bcc strains have emerged as problematic opportunistic pathogens in both, cystic fibrosis patients, chronic granulomatous disease and nosocomial outbreaks. The inherent pathogenic potential of biotechnologically interesting strains is preventive of their wide-spread application. Like many Gram-negative bacteria, Bcc strains employ cell-to-cell communication ("quorum sensing"; QS) systems to express various functions in a population density-dependent manner. Previous work has demonstrated that the production of proteases, chitinases, and siderophores, motility, biofilm formation and virulence is QS-regulated in Bcc strains. This project aims at identifying those QS-dependent functions that are important for biofilm formation and pathogenicity. The specific aims are:o To define the QS regulon of B. cenocepacia H111 by the aid of a combined transcriptomic and proteomic approacho To identify regulators affecting the CepIR signaling systemo To identify QS-regulated genes required for biofilm formation and to determine their role in biofilm developmento To identify QS-regulated virulence factors and to assess their importance in different infection modelsTo address these questions we will employ classic genetic methods in combination with transcriptomics, proteomics as well as wit transcriptome and proteome data with phenotypic microarrays. Biofilms will be cultivated in artificial flow chambers and virulence of strains will be assayed in two non-mammalian infection models, using the nematode Caenorhabditis elegans and the larvae of the greater wax moth Galleria mellonella. The proposed work program aims at the identification of global regulators affecting QS and QS-regulated factors required for biofilm formation and pathogenicity. This line of research may therefore also lead to the identification of novel targets for the development of antibacterial drugs. Furthermore, knowledge of the virulence factors of Burkholderia is a crucial prerequisite for the assessment of the potential risks associated with strains showing promise in biotechnological applications.