Bacillus subtilis Strains with Antifungal Activity against the Phytopathogenic Fungi

Bacillus strains isolated from the rhizosphere soil of potato roots were evaluated for the potential antagonistic activity against fungal pathogens in vitro and in vivo. Two bacterial isolates were identified as new Bacillus subtilis strains by 16S rRNA and GyrB gene sequencing and were designated GM2 and GM5, respectively. Strains were characterized by their ability to inhibit growth of a number of phytopathogenic fungi. It was shown that GM5 strain inhibited growth of phytopathogenic fungi more effectively than GM2 strain. Both strains were capable of producing a number of hydrolytic enzymes as well as antimicrobial metabolites (ammonia and HCN). In addition, GM2 strain also produced siderophores. Four genes encoding antimicrobial peptides were identified in the genome of GM2 strain: ituC, bmyB, bacA and srfA. Genome of GM5 contained two genes encoding for antimicrobial peptides, srfA and fenD. Purified lipopeptide fraction from GM5 but not from GM2 strain was able to control Fusarium solani spread in the plate assay. Furthermore, Bacillus subtilis strain GM2 promoted growth of wheat but only GM5 strain was able to protect wheat seedlings from Fusarium oxysporum infection.