Molecular detection of antibiotic related genes from Pseudomonas aeruginosa FP6, an antagonist towards Rhizoctonia solani and Colletotrichum gloeosporioides

Despite the importance of antibiosis in biological control, little is known about the genes involved in antifungal activity. Therefore, the present study was aimed at identifying the location of the antagonistic gene(s) in Pseudomonas aeruginosa FP6 towards Rhizoctonia solani and Colletotrichum gloeosporioides using a PCR-based approach. A new bacterial strain, designated as FP6, was isolated from rhizospheric soil and identified as a member of Pseudomonas aeruginosa based on 16S rRNA analysis. The secondary metabolites produced by this strain have shown broad-spectrum antifungal activity against Rhizoctonia solani and Colletotrichum gloeosporioides. Antifungal metabolites of a nonenzymatic nature were found to be responsible for the antagonism. Hyphal malformation was also observed in both of the fungal pathogens. PCR analysis of the genomic DNA with antibiotic specific primers detected phenazine-l-carboxylic acid, 2,4-diacetylphloroglucinol, and pyoluteorin. Plasmid isolation and plasmid curing of the strain exhibited varied antagonistic activity. A chromosomal gene was found to be involved in the production of a fungal antagonistic compound as demonstrated by the gel elution technique using antibiotic gene-specific primers. The study speculates that antimetabolites play an important role in the control of phytopathogens.