P-320 - Diversity of putative contact-dependent inhibition systems in Ralstonia

Bacterial contact-dependent inhibition (CDI) systems mediate antagonistic interactions via receptor-dependent toxin delivery into recipient cells. Previously characterized CDI loci minimally encode the extracellular toxin delivery protein CdiA, the transporter CdiB and cognate immunity protein CdiI. We identified CdiA and CdiB homologs in Ralstonia pseudosolanacearum, an aggressive soil-borne pathogen that causes wilting disease in diverse plants. This species has an expanded number of putative CDI loci, which cluster into four distinct families. Each family varies in their genomic context, number of duplications and locus architecture. Recombination events overlapping with cdiA and cdiI indicate increased diversification at toxin-immunity domains. We are currently investigating how strains that share or vary in putative CDI loci perform in direct competition in vitro and in planta using co-culturing and co-infection assays. This work will contribute to our understanding of how CDI systems mediate pathogenicity and interbacterial interactions in R. pseudosolanacearum.