Interplay between extracellular matrix components of Pseudomonas putida biofilms

The extracellular matrix of bacterial biofilms has at least two key functions: to serve as a structural scaffold for the multicellular community, and to play a protective role against external stress. In this work, we report a compensatory effect whereby Pseudomonas putida reacts to the lack of either of the two main surface proteins involved in biofilm formation, LapA and LapF, by increasing expression and production of a species-specific EPS. Elevated levels of the second messenger molecule cyclic di-GMP alter the balance of extracellular matrix components, and the phenotypes of lapA and lapF mutants under these conditions are indicative of direct interactions taking place between large secreted proteins and exopolysaccharides. Our data suggest the existence of a mechanism by which bacteria would sense alterations in the composition of the extracellular matrix, leading to changes in expression of the different elements. © 2013 Institut Pasteur.Work supported by grant BFU2010-17946 from the Plan Nacional de I+D+I and EDFR. MMG is the recipient of a FPI fellowship. REdC is funded by CONICET as a Career Investigator. We thank T. Tolker-Nielsen for providing EPS mutant strains and A. Rodríguez at the Microscopy Service of the Estación Experimental del Zaidín for help with electron microscopy.Peer Reviewe