Characterizing a novel strain of Bacillus amyloliquefaciens BAC03 for potential biological control application

Aims To identify and characterize a bacterial strain BAC03, evaluate its biological control activity against potato common scab (Streptomyces spp.) and characterize an antimicrobial substance produced by BAC03. Methods and Results Bacterial strain BAC03, isolated from potato common scab suppressive soil, was identified as Bacillus amyloliquefaciens by analysing sequences of fragments of the recA, recN, cheA and gyrA genes. BAC03 displayed an antagonistic activity against Streptomyces spp. on agar plates using a co-culture method. In glasshouse assays, BAC03 applied in potting mix significantly reduced common scab severity (P<0.05) and potentially increased the growth of potato plants (P<0.05). An antimicrobial substance extracted from BAC03 by ammonium sulfate precipitation was identified as an LCI protein using liquid chromatographymass spectrometry. The antimicrobial activity of either a BAC03 liquid culture or the ammonium sulfate precipitate fraction was stable under a wide range of temperatures, and pH levels, as well as following incubation with several chemicals, but was reduced by all proteinases tested. Conclusions Bacillus amyloliquefaciens strain BAC03 displayed a strong antimicrobial activity, that is, the suppression of potato common scab, and may potentially enhance the plant growth. LCI protein is associated with some of the antimicrobial activity. Significance and Impact of the Study Bacterial strain BAC03 has the potential to be developed as a commercial biological control agent for potato common scab.