The Isolation and Characterization of Acidovorax and Brevundimonas Bacteriophages with Preliminary Biocontrol Study on Arabidopsis thaliana

As antibiotic-resistance becomes an increasing global concern, researchers are looking for alternatives to combat phytopathogenic rhizobacteria – one of which is through the application of phage biocontrol. To elucidate the complex tripartite relationships between phage, bacteria and plant interactions, nine novel phages were isolated from potential phytopathogenic strains of Acidovorax (RBW13) and Brevundimonas (RBW18). These phages were isolated from root samples obtained from the Rocky Branch Creek and the Broad River located in Columbia, SC. Using Pulsed-Field Gel Electrophoresis (PFGE), we identified seven “medium sized” phages (~40 kbp), one “large-sized” phage (~200 kbp), and one “small-sized” phage ( < 25 kbp). Three phages were determined to be lambda-like due to their “ladder-building” patterns on PFGE. Although spot-tests revealed that all phages seemed to have broad host ranges that spanned over multiple genera, plaque-formations must be observed in future experiments to determine if these phages can infect their hosts productively. Preliminary in planta experiments were performed on Arabidopsis thaliana under the following conditions: water-only, bacteria-only, and phage- bacteria. Three RBW18 phages (R5, R6, and R7) were used for these experiments. The Brevundimonas strain RBW18 showed statistically significant inhibitory effects on the A. thaliana’s vertical root development after 13 days of germination. Plants treated with R5 and R7 phages exhibited statistically significant improvements on A. thaliana’s vertical root development after 13 days of germination. While plants treated with R6 also showed improvements in root growth, it was not statistically significant. None of the phages were successful in producing bactericidal effect, thus phage infection optimizations are required. These phages showed promising potentials to be used for phage biocontrol; however, further studies are required to enhance their effectiveness.