DSSS - (Bacterial) Sex and Death: Contact-dependent antagonism in plant pathogenic Ralstonia sp.

Microbes have evolved multiple strategies to compete for access to scarce resources. Contact-dependent inhibition (CDI) is a mechanism of inter-bacterial antagonism mediated by two-partner secretion systems comprised of a transporter, toxin-encoding extracellular protein and cognate immunity protein. I will present work from our lab showing plant pathogenic Ralstonia spp. possess the largest CDI repertoires yet described, with toxin-immunity gene modules rapidly exchanged via recombination. We show that multiple loci within a single strain function in self-recognition and non-self antagonism. These interactions are highly specific, even between CDI of the same type, and result in competitive exclusion during plant host infection. Remarkably, the expansion of CDI carriage in Ralstonia sp. is driven by prophage, which form tandem arrays in hotspots of chromosomal integration. Bacteriophage infection may thus drive rapid changes in the population structure of bacterial pathogens, altering infection outcomes in eukaryotic hosts.