BAOBAB

Many bacteria secrete small peptides with antimicrobial properties called bacteriocins that contribute to their competitiveness in the environment. The spectrum of action of bacteriocins is narrow and most often targets genetic lineages of the same bacterial species. Therefore, bacteriocins have already found their application in food industry as natural preservatives, in animal production as probiotics and they represent a credible alternative to antibiotics and constitute a serious solution to multidrug-resistant bacteria. In agriculture, although many diseases are caused by bacteria attacking plants, studies on bacteriocins are still very limited. The bacterial Ralstonia solanacearum species complex (RSSC) is the causal agent of bacterial wilt, one of the most important disease of crop plants worldwide and is included in the A2 (high risk) list of quarantine organisms in Europe. Recently we showed that the two RSSC lineages, I-18 and I-31, mostly prevalent in the South-West Indian Ocean (SWIO) have bacteriocin-like activity against less prevalent lineages suggesting a role for these molecules in the epidemic success. Interestingly, the bacteriocin activities of some I-18 strains target the I-31 lineage which is a considerable threat to solanaceous crops in the small islands of the SWIO and in Africa. The objectives of the BAOBAB project are : (i) to widely screen the diversity of RSSC strains for their ability to produce bacteriocins (ii) to characterize for the first time bacteriocins from the RSSC, using both a biochemical purification pipeline based on bio-guided fractionation, and genomic comparison methods to identify bacteriocin-encoding genes, (iii) to estimate their role in the success of epidemic strains by performing competition assays between active and susceptible strains or depleted mutants for bacteriocins (iv) to provide a proof of concept for the use of bacteriocins as efficient biocontrol agent to prevent bacterial infections in plants.