The global carbon metabolism regulator Crc is a component of a signal transduction pathway required for biofilm development by Pseudomonas aeruginosa

The transition from a planktonic (free-swimming) existence to growth attached to a surface in a biofilm occurs in response to environmental factors, including the availability of nutrients. We show that the catabolite repression control (Crc) protein, which plays a role in the regulation of carbon metabolism, is necessary for biofilm formation in Pseudomonas aeruginosa, Using phase-contrast microscopy, we found that a cre mutant only makes a dispersed monolayer of cells on a plastic surface but does not develop the dense monolayer punctuated by microcolonies typical of the wild-type strain. This is a phenotype identical to that observed in mutants defective in type TV pilus biogenesis, Consistent with this observation, cre mutants are defective in type IV pilus-mediated twitching motility, We show that this defect in type IV pilus function is due (at least in part) to a decrease in pill (pilin) transcription. We propose that nutritional cues are integrated by Crc as part of a signal transduction pathway that regulates biofilm development.