Tailocin-mediated interactions among Soft RotPectobacteriaceae

Abstract

Bacteria often carry phage-derived elements within their genomes, some of which can produce phage-like particles (tailocins) used as weapons to kill kin strains in response to environmental conditions. This study investigates the production and activity of such particles by plant pathogenic bacteria belonging to the Pectobacterium, Dickeya, and Musicola genera that often compete for the same niche, providing an attractive model to study the ecological role of tailocins. Transmission electron microscopy (TEM) revealed that most analyzed strains (88%) produced tailocins. Tailocin-mediated killing interactions were assessed across 351 strain pairs, showing that Dickeya spp. had a higher incidence of killing (57.1%) than Pectobacterium spp. (21.6%). Additionally, Dickeya spp. strains exhibited inter-genus activity, targeting both Pectobacterium spp. and Musicola sp., while Pectobacterium spp. tailocins were genus-specific. A so-called "bilateral killing" was observed in 33.9% of interactions, predominantly within Dickeya spp. Although tailocins were morphologically indistinguishable between producer strains, genomic analyses identified conserved tailocin gene clusters across both genera, with distinct structural differences between Pectobacterium spp. and Dickeya spp tailocins. This suggests different origins of these particles. Induction experiments demonstrated that tailocin production was significantly boosted by hydrogen peroxide, supporting the potential role of these particles in bacteria-bacteria competition during infection. Lastly, tailocin production was detectable in infected potato tissue but not in river water, highlighting the ecological relevance of tailocins in plant environments.