Résumé
Microorganisms produce a variety of molecules to interact with their hosts. Xenorhabdus is an entomopathogenic bacterium involved in a symbiotic relationship with Steinernema nematodes. Throughout its intricate life cycle, Xenorhabdus synthesized a multitude of metabolites via Non-Ribosomal-Peptide Synthetases (NRPSs). PAX cyclolipopeptides are a family of NRP-type metabolites whose role remains poorly understood. This study elucidates the multifaceted role of PAX peptides in the life cycle of Xenorhabdus. By mass spectrometry, we dynamically characterized the presence of PAX peptides from the early pathogenic stage to the late necrotrophic stage of the Xenorhabdus life cycle. We also showed that a PAX peptide-deficient mutant, ΔpaxA exhibited reduced biofilm formation and enhanced swimming motility. Additionally, PAX peptides were shown to promote the emergence of Steinernema infective juveniles in vivo. Through in vitro rearing on lipid agar, we observed a developmental defect in adult nematodes in the presence of the ΔpaxA mutant, which was rescued by the addition of synthetic PAX peptides. Furthermore, we established that the ability to produce PAX peptide is both restricted to and widespread within Xenorhabdus genus. Together, these findings demonstrate the involvement of PAX peptides in the mutualistic interaction between the bacterium Xenorhabdus and its nematode partner, paving the way for further understanding of NRP-type peptide ecological roles.