Phenotypic and Genotypic Characterization of Newly Isolated <i>Xanthomonas euvesicatoria</i>-Specific Bacteriophages and Evaluation of Their Biocontrol Potential

Abstract

Bacteriophages have greatly engaged the attention of scientists worldwide due to the continuously increasing resistance of phytopathogenic bacteria to commercially used chemical pesticides. However, the knowledge regarding phages is still very insufficient and must be continuously expanded. This paper presents the results of the isolation, characterization, and evaluation of the potential of 11 phage isolates as natural predators of a severe phytopathogenic bacterium—Xanthomonas euvesicatoria. Phages were isolated from the rhizosphere of tomato plants with symptoms of bacterial spot. The plaque morphology of all isolates was determined on a X. euvesicatoria lawn via a plaque assay. Three of the isolates were attributed to the family Myoviridae based on TEM micrographs. All phages showed good long-term viability when stored at 4 °C and −20 °C. Three of the phage isolates possessed high stability at very low pH values. Fifty-five-day persistence in a soil sample without the presence of the specific host and a lack of lytic activity on beneficial rhizosphere bacteria were found for the phage isolate BsXeu269p/3. The complete genome of the same isolate was sequenced and analyzed, and, for the first time in this paper, we report a circular representation of a linear but circularly permuted phage genome among known X. euvesicatoria phage genomes.

Keywords

• <i>Myoviridae</i> bacteriophages
• bacterial spot disease
• <i>Xanthomonas euvesicatoria</i>
• circular genome permutation
• rhizosphere