Genomic and phenotypic characterization of Vibrio proteolyticus and its postbiotic potential

Vibrio proteolyticus DCF12.2, isolated from the intestinal tract of the flatfish Dicologlossa cuneata , was characterized through integrated genomic and phenotypic analyses to assess its antimicrobial activity, biosynthetic potential and resistance- and virulence-related features. Genome-based analyses supported its assignment to V. proteolyticus and identified biosynthetic gene clusters associated with arylpolyene, nonribosomal peptide (NRP)-metallophore/amphibactin, ectoine and ribosomally synthesized and posttranslationally modified peptide/nonribosomal peptide synthetase (RiPP-/NRPS)-like pathways, together with numerous predicted antimicrobial peptide candidates. The resistome was mainly composed of chromosomal efflux- and target-associated determinants, whereas virulence-related hits were largely restricted to functions linked to motility, chemotaxis and secretion. The genome also contained sequences homologous to proteins previously described in Photobacterium damselae subsp. piscicida and Vibrio harveyi , as well as three prophage regions and multiple genomic islands (GIs). Phenotypic assays showed that the strain and/or its extracellular products (ECPs) inhibited P. damselae subsp. damselae , V. harveyi and Aeromonas hydrophila . The inhibitory activity of the ECPs against P. damselae subsp. damselae was maintained after incubation at 37 °C and after acidification to pH 5. In conclusion, although the strain exhibits antimicrobial activity and other characteristics that would qualify it a probiotic candidate, the presence of certain virulence factors makes it more suitable for use as a postbiotic. Key points DCF12.2 shows broad genomic potential for antimicrobial compound production Extracellular products inhibit relevant aquatic bacterial pathogens Virulence-related traits support postbiotic rather than probiotic use