BdlA, a Chemotaxis Regulator Essential for Biofilm Dispersion in Pseudomonas aeruginosa

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Abstract
Multiple environmental cues have been shown to trigger biofilm detachment, the transition from surface-attached, highly organized communities known as biofilms to the motile lifestyle. The goal of this study was to identify a gene product involved in sensing environmental cues that trigger biofilm dispersion in Pseudomonas aeruginosa . To do so, we focused on novel putative chemotaxis transducer proteins that could potentially be involved in environmental sensing. We identified a locus encoding such a protein that played a role in detachment, as indicated by the observation that an isogenic mutant biofilm could not disperse in response to a variety of environmental cues. The locus was termed bdlA for b iofilm d ispersion l ocus. The BdlA protein harbors an MCP ( m ethyl-accepting c hemotaxis p rotein) domain and two PAS ( P er- A rnt- S int) domains that have been shown to be essential for responding to environmental signals in other proteins. The dispersion-deficient phenotype of the bdlA mutant was confirmed by treatment with the biocide H 2 O 2 and by microscopic observations. The dispersion response was independent of motility. bdlA mutant biofilms were found to have increased adherent properties and increased intracellular levels of cyclic di-GMP (c-di-GMP). Our findings suggest that BdlA may be a link between sensing environmental cues, c-di-GMP levels, and detachment. Based on our findings, a possible involvement of BdlA in a signaling cascade resulting in biofilm dispersion is discussed.