Biocontrol potency of Bdellovibrio bacteriovorus toward exo-biopolymer producing phytopathoges: in vitro and in vivo assessments

BACKGROUND AND ABJECTIVEBdellovibrios are predatory bacteria that invade other live Gram-negative bacterial cells for growth and reproduction. They have recently been considered as potential living antibiotics and biocontrol agents. In this study, the predatory activity and biocontrol potency of Bdellovibrio bacteriovorus strain SOIR-۱ against Pantoea sp. strain BCCS and Xanthomonas campestris, two exobiopolymer-producing phytopathogens, was evaluated.MATERIALS AND METHODSPlaque formation assays and lysis analysis in the broth co-cultures were used for the in vitro evaluation of bacteriolytic activity of strain SOIR-۱. The in vivo biocontrol potential of strain SOIR-۱ was evaluated by pathogenicity tests on the onion bulbs and potato tuber slices. The phytopathogens were also recovered from the infected plant tissues and confirmed using biochemical tests and PCR-based ۱۶S rRNA gene sequence analysis.RESULTS AND DISCUSSIONTypical bdellovibrios plaques were developed on the lawn cultures of Pantoea sp. BCCS and X. campestris. The killing rate of strain SOIR-۱ toward Pantoea sp. BCCS and X. campestris was ۸۴.۳% and ۷۶.۳%, respectively. Exo-biopolymers attenuated the predation efficiency of strain SOIR-۱ up to ۱۰.۲–۱۸.۲% (Pantoea sp. BCCS) and ۱۲.۲–۱۷.۳% (X. campestris). The strain SOIR-۱ significantly reduced rotting symptoms in the onion bulbs caused by Pantoea sp. BCCS (۶۹.۰%) and potato tuber slices caused by X. campestris (۷۳.۱%).CONCLUSIONAlthough more field assessments are necessary, strain SOIR-۱ has the preliminary potential as a biocontrol agent against phytopathogenic Pantoea sp. BCCS and X. campestris, especially in postharvest storage. Due to the particular physicochemical properties of evaluated exobiopolymers, they can be used in the designing encapsulation systems for delivery of bdellovibrios.