Screening for antibacterial molecules in meiobenthic nematodes belonging to the Oncholaimidae family

Active substances such as antimicrobial peptides (AMPs) defined as antibiotics naturally produced by all living species, have already been characterized and identified from various marine organisms (fish, sponges, annelids, echinoderms, crustaceans, molluscs and tunicates) except from nematodes. In this study, we investigated the biochemical isolation of antibacterial substances from three free-living marine nematodes belonging to the Oncholaimidae family that dominated meiofauna of two coastal environments characterized by reduced and hypoxic sediments with high concentration of sulfides (Roscoff Harbour in France and Secca delle Fumose in Italy). There are no consensus sequences for AMPs which are even more diversified in the marine environment compared to the terrestrial one. A bioassay guided purification protocol was used since it constitutes the only method to find novel active peptides. Data showed the potential of two of the three nematodes species as interesting sources of small sized antibiotics. The third species showed an occasional epi-symbiotic association with filamentous bacteria, but singularly lacked antimicrobial activity. The lack of biological material did not allow the identification of the antimicrobial molecules.