Biofilm dispersal: deciding when it is better to travel

Summary Bacteria live predominantly in biofilms, and the internal signal cyclic diguanylate (c‐di‐ GMP ) is a universal signal that governs the formation and the dispersal of these communities. P seudomonas aeruginosa is one of the most important reference systems for studying bacterial biofilms and contains numerous diguanylate cyclases ( DGCs ) for synthesizing c‐di‐ GMP and phosphodiesterases ( PDEs ) for degrading c‐di‐ GMP . However, few studies have discerned how cells in biofilms respond to their environment to regulate c‐di‐ GMP concentrations through this sophisticated network of enzymes. B asu R oy and S auer (2014) provide insights on how cells disperse in response to an increase in nutrient levels. Their results show that the inner membrane protein NicD is a DGC that controls dispersal by sensing nutrient levels: when glutamate concentrations are increased, NicD is dephosphorylated, which increases c‐di‐ GMP levels and leads to phosphorylation and processing of dispersal regulator BdlA . Processing of BdlA leads to activation of PDE DipA , which results in a net reduction of c‐di‐ GMP and biofilm dispersal. These results suggest biofilm dispersal relies on surprisingly dynamic c‐di‐ GMP concentrations as a result of a sophisticated interaction between DGCs and PDEs .