Background and Aim : Bdellovibrio-and-like organisms (BALOs) are a group of predatorymicroorganisms that attack and kill other Gram-negative bacteria for growth and reproduction,acting as potential living antibiotics and biocontrol agents. This study describes the isolation,identification, biological properties, and bacteriolytic activity of the first Bdellovibrio sp. with abroad prey range from Iran.Methods : One BALO strain with high predatory potency was isolated from the rhizosphere soilusing Escherichia coli as prey. It was identified and designated as
Bdellovibrio bacteriovorus strainSOIR-۱ through plaque assays, biological properties, transmission electron microscopy (TEM),Bdellovibrio-specific PCRs, and ۱۶S rRNA gene sequence analysis. The antibiotic resistancepattern of some clinically isolated Gram-negative pathogens was determined through the standardKirby-Bauer disc diffusion method. Finally, the predatory potency and bacteriolytic activity ofSOIR-۱ toward some Enterobacteriaceae members and antibiotic-resistant clinical pathogens wasalso evaluated through the plaque formation assays and lysis analysis in the broth co-cultures,followed by monitoring the OD۶۰۰, CFU/ml, and PFU/ml parameters.Results : TEM, Bdellovibrio-specific PCRs, and analysis of ۱۶S rRNA gene sequence revealedthe close relationship of SOIR-۱ with strains of Bdellovibrio bacteriovorus. The strain SOIR-۱grew within the temperature range of ۲۵-۳۷ °C and the pH range of ۶.۰-۸.۰, with the optimalpredatory activity at ۳۰ °C and pH ۷.۴. It had the highest and lowest predatory activity towardShigella dysenteriae and Pseudomonas aeruginosa with a killing rate of ۸۹.۶۶% and ۷۴.۸۳%,respectively. All clinical isolates showed the properties of extensively drug-resistant (XDR).Regarding the XDR clinical isolates, SOIR-۱ showed the highest and lowest bacteriolyticefficiency against Acinetobacter baumannii (۸۴.۳۳%) and Pseudomonas aeruginosa-۳۶۹(۵۵.۱۶%), respectively.Conclusion : Considering the hypothesis of Bdellovibrios heterogeneity, identification of newisolates contributes to a deeper understanding of their diversity, their ecological roles in differentecosystems, and their promising potential as living antibiotics or biocontrol agents. Bdellovibrioswith broad bacteriolytic nature has not previously been reported in sufficient detail from Iran. Theresults of this study showed the great potential of native B. bacteriovorus SOIR-۱ as a livingantibiotic in the control and treatment of diseases caused by Enterobacteriaceae as well as GramnegativeXDR pathogens, regardless of their antimicrobial resistance state.