Antifungal peptides produced by Bacillus amyloliquefaciens AG1 active against grapevine fungal pathogens

Antifungal metabolites produced by Bacillus amyloliquefaciens AG1, previously isolated from wood of grapevine with esca syndrome, were studied. The crude protein extract (CPE) obtained from culture supernatant fluid by precipitation with ammonium sulfate was assayed against many grapevine fungal pathogens. B. amyloliquefaciens strain AG1 showed a broad spectrum of antifungal activity, inhibiting mycelial growth in vitro of all tested fungal microorganisms. The metabolites contained in CPE were heat stable and remained active over a wide pH range (2-10). Their activity was not affected by proteolytic or glycolytic enzymes. Tricine-SDS-polyacrylamide gel electrophoresis revealed a single band within the range of 2,510-3,480 Da, that showed inhibitory activity when used in the antifungal assay. Mass spectrometry analysis of this band allowed the substances involved in antibiosis to be identified as two tryptic peptides that correspond to the N-terminal sequence of subtilisin BPN'. These results suggest a potential role of B. amyloliquefaciens AG1 as a biocontrol agent.