[Purification and properties of antifungal protein X98III from Bacillus subtilis]

Bacillus subtilis BS-98 is one of the antagonistic strains strongly against plant fungal pathogens such as Physalospora piricola Nose. The antifungal protein was purified by ammonium sulphate precipitation and column chromatography on Sephadex G-100 and DEAE-cellulose, and it was named X98III. Molecular weight of X98III is 59,000 by SDS-PAGE and PI value is 4.50 by PAG-IEF, respectively. X98III was demonstrated as glycoprotein and lipoprotein by CAM (cellulose acetate membrane) electrophoresis and special staining. We estimated it contains 6% saccharides by using DNS methods. This protein was also found to be thermostabale and partially sensitive to proteinases. The amino acid analysis of the protein X98III showed that it comprises of 11 different amino acids and Glu, Tyr, Cys are the abundant amino acids. No Asp, Phe and Met were found. Purified X98III has strong inhibiting activity against the pathogens of Physalospora piricola, Phoma asparagi, etc. The antifungal mechanism of X98III was mainly disintegration of the cell wall to make the hyphae abnormal and the spores germinate abnormally or can not germinate at all.