A Psl-like polysaccharide has a key role in the biofilm architecture of two plant-associated Pseudomonas

Abstract

The Psl polysaccharide has only been studied in Pseudomonas aeruginosa, and its role in bacteria that interact with plants is still unknown. On the one hand, P. syringae is a model of study of plant-pathogen interactions. On the other hand, P. chlororaphis is a biocontrol agent of plant-fungal diseases, as the white root rot caused by Rosellinia necatrix. In silico analysis have let us identify in both species a genomic region which is ortholog to the Psl-encoding region of P. aeruginosa PAO1. We constructed mutants of this region in both strains and analysed its phenotype in biofilm formation, both in static microwell plates and dynamic flow-cell chamber experiments. The results revealed a different and an important role of this polysaccharide in the biofilm architecture of both strains. Furthermore, in P. syringae this Psl-like polysaccharide has a very important role in swarming motility. All these striking phenotypes led us further study the implication of this polysaccharide in the lifestyles of both models of plant-bacteria interaction.