Characterization of site-directed mutants defective in HPR productionof P. fluorescens PCL1606 and its role in biocontrol

Abstract: Pseudomonas fluorescens PCL1606 is a rhizobacteria with biocontrol activity againstmany soil-borne phytopathogenic fungi. Its antagonist activity strongly correlates with theproduction of the antibiotic 2-hexyl, 5-propyl resorcinol (HPR). However, other antibiotics couldbe detected in P. fluorescens PCL1606, such as pyrrolnitrin (PRN) and hydrogen cyanide (HCN),and could be also related to its antagonist activity. To determine the role of these antibiotics onbiocontrol, a collection of mutants in different antibiotics was initiated, studying in first place thegenes involved in the production of HPR. A collection of site-directed mutants to thehomologous dar operón, related to the HPR production in P. fluorescens PCL1606, have beenconstructed. Characterization of the potential traits involved in the biocontrol activity of thesederivative strains were performed, including antagonism, motility, production of signal molecules,biofilm formation and biocontrol. Our results showed a role of some of the dar genes in thebiocontrol.