Abstract:
Pectobacterium brasiliense (Pbr) 1692 is an aggressive phytopathogen affecting a broad host
range of crops and ornamental plants, including potatoes. Previous research on animal pathogens,
and a few plant pathogens, revealed that Outer Membrane Vesicles (OMVs) are part of Gram-negative
bacteria’s (GNB) adaptive toolkit. For this reason, OMV production and subsequent release from
bacteria is a conserved process. Therefore, we hypothesized that OMVs might transport proteins that
play a critical role in causing soft rot disease and in the survival and fitness of Pbr1692. Here, we show
that the potato pathogen, Pbr1692, releases OMVs of various morphologies in Luria Bertani media at
31 C. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) confirmed
the production of OMVs by Pbr1692 cells. Transmission Electron Microscopy showed that these
exist as chain-, single-, and double-membrane morphologies. Mass spectrometry followed by Gene
Ontology, Clusters of Orthologous Groups, Virulence Factor, CAZymes, Antibiotic Resistance Ontology,
and Bastion6 T6SE annotations identified 129 OMV-associated proteins with diverse annotated
roles, including antibiotic stress response, virulence, and competition. Pbr1692 OMVs contributed
to virulence in potato tubers and elicited a hypersensitive response in Nicotiana benthamiana leaves.
Furthermore, Pbr1692 OMVs demonstrated antibacterial activity against Dickeya dadantii.
