I. (Irene) de Bruijn: “Natural detergents produced by beneficial soil bacteria”

Cyclic lipopeptides (CLPs) are natural detergents produced by a variety of microorganisms, including yeasts, fungi and bacteria. These soap-like compounds have diverse function for the producing bacterial strains, including a role in motility, attachment/detachment to surfaces, virulence, antimicrobial activity, but also in protection against protozoan predation. This PhD research project focused on two structurally related CLPs, designated massetolide and viscosin, produced by the soil-bacterium Pseudomonas fluorescens. Massetolide and viscosin were shown to protect tomato plants against infection by the notorious late-blight pathogen Phytophthora infestans, but also cucumber plants against the damping-off pathogen Pythium. Both CLPs also play a crucial role in swarming motility and biofilm formation of Pseudomonas fluorescens. Molecular analyses further revealed that several genes are involved in the regulation and biosynthesis of these natural bacterial soaps and that specific environmental signals trigger the production of these versatile compounds.