Tailocin-Mediated Interactions Among Soft Rot Pectobacteriaceae

Bacteria 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 tailocins by plant-pathogenic bacteria: Pectobacterium, Dickeya, and Musicola genera, which compete for niche, providing an attractive model to study the ecological role of tailocins. Microscopy revealed that most analysed strains (88%) produced tailocins. Tailocin-mediated killing interactions were assessed across 351 strain pairs, showing that Dickeya spp. had a higher likelihood of killing neighbours (57.1%) than Pectobacterium spp. (21.6%). Additionally, Dickeya spp. strains exhibited broader phylogenetic killing, targeting both Pectobacterium spp. and Musicola sp., while Pectobacterium spp. tailocins were genus-specific. The mutual (bilateral) killing was observed in 33.9% of interactions, predominantly within Dickeya spp. Although tailocins were morphologically indistinguishable between producers, genomic analyses identified conserved clusters having diverse structural and organisational differences between Pectobacterium spp. and Dickeya spp. tailocins. This suggests different origins of these particles. Induction experiments demonstrated that tailocin production was boosted by hydrogen peroxide, supporting the role of these particles in bacteria–bacteria competition during plant infection when plants produce ROS to protect themselves from pathogens. Tailocins were detectable in infected potato tissue but not in river water, highlighting the particular ecological relevance of tailocins in these studied environments.