[Purification and characterization of a novel antifungal peptide APS-1 produced by Bacillus cereus]

In previous study, we isolated an antagonist Bacillus cereus strain: S-1 from cotton plant. In field experiments, this bacterium was shown strong inhibition to several plant diseases. In this paper, we reported the purification of the antifungal substance produced by the bacterium and its properties. After the steps of acid precipitation, methanol and ethy lether extraction, Sephadex G100 and DEAE52 column chromatography, the antifungal material was purified. The purified material had absorption peak at 275 nm, and was exhibited negative in biuret color reaction. However after hydrolyzed with HCl, this substance shown positive in the same reaction. Amino acid analysis to the hydrolysate of APS-1 showed that APS-1 was composed of Glu, Asp, Tyr, Ser, Thr, Pro, Leu, Ile, Val and an unknown amino acid. Combining with its pratial resistance to proteinases, it was suggested that this antifungal material was a cyclic peptide. This peptide, named APS-1, with strong inhibition on the germination of spores of the phytopathogens tested, was shown high stability against ultraviolet radiation and heat. APS-1 may have potential role in plant diseases biological control.