Fluorescent pseudomonads are ubiquitous gram-negative bacteria able to thrive in very different environments (plant roots, water, polluted soils, mammal host...). As an example, the type species Pseudomonas aeruginosa is known as a pathogen for man but also as a plant-beneficial micro-organism of the rhizosphere. One of the main factors for the survival of fluorescent pseudomonads such as P. aeruginosa and P. fluorescens, is the existence of a siderophore (pyoverdine)-mediated high-affinity iron transport system which allows these bacteria to compete with micro-organisms for iron and to colonise tissues in which iron is not freely available. Our research programme aims at unravelling the mechanisms involved in siderophore-mediated iron uptake in P. aeruginosa (human pathogen, plant beneficial) and P. fluorescens (plant beneficial), as well as adopt these insights towards applications in medicine and plant biocontrol. Recent experimental evidence indeed suggests that targeted interference with siderophore-mediated iron-uptake represents a promising avenue for the development of novel antibiotics. The study of the interaction of fluorescent pseudomonads with plants aims at the possible development of biocontrol agents against different plant root pathogens. Here we focus on the regulation of the production of antifungal molecules such as phenazines. Finally, we also investigate the potential of these antifungal molecules, and more particularly pyocyanine, to induce systemic resistance in plants against foliar pathogens.