Bacteriocinogenesis in cells of Xenorhabdus nematophilus and Photorhabdus luminescens: Enterobacteriaceae associated with entomopathogenic nematodes

Summary— Xenorhabdus nematophilus FI strain and Photorhabdus luminescens NC19 strain produced bacteriocins after mitomycin C treatment and under natural conditions respectively. The ultrastructure of these two strains was described and compared to the ultrastructure of untreated or normal cells. After image processing of purified bacteriocins we found morphological homology in infected cells with protoplasmic rods in longitudinal section and hexagonal aggregates in transversal section. We concluded that these particular structures, so‐called ‘lattice structures’ and previously interpreted as ‘photosomes’, are in fact the early stages of in situ production of bacteriocins in these two bacterial genera. Natural occurrence of Photorhabdus spp bacteriocinogenesis was observed in other strains, while other lysogenic strains of Xenorhabdus spp are lysed after a mitomycin C treatment.