Identification of Pantoea ananatis strain BCA19 as a potential biological control agent against Erwinia amylovora

In this study, we aimed to screen potential antagonistic microorganisms against <i>Erwinia amylovora</i>, the causal agent of fire blight. From 127 unknown bacterial isolates tested, 2 bacterial strains (BCA3 and BCA19) were identified to show distinct antagonistic activity against <i>E. amylovora</i> in agar plate assay. Phylogenetic analysis of the 16s rRNA sequence identified both BCA3 and BCA19 as <i>Pantoea ananatis</i>. Among these BCA19 showed 13.9% stronger antagonistic activity than BCA3. Thus we further characterized antagonistic activity of BCA19. Culture filtrates (<i>CF</i>) of BCA19 significantly inhibited the swimming and swarming motility of <i>E. amylovora</i>. Ethyl acetate and n-butanol extracts of <i>CF</i> of BCA19 exhibited antibacterial activity in disk diffusion assay. Furthermore, gas chromatography-mass spectrometry analysis of ethyl acetate and n-butanol extracts of <i>CF</i> of BCA19 identified antibacterial compounds, including indole and hexahydropyrrolo[1,2-a]pyrazine-1,4-dione. Importantly, indole inhibited growth of <i>E. amylovora</i> with IC₅₀ value of 0.109 ± 0.02 mg/mL (~930.4 μM). Whole genome sequence analysis of BCA 19 revealed gene clusters related with siderphore, andrimid, arylpolyene and carotenoid-type terpene production. This study indicates that BCA19 can be used as a potential biological control agent against <i>Erwinia amylovora</i>.