Identification and characterization of antifungal compounds from a Burkholderia strain against plant pathogenic fungi

Abstract

Aims: Biocontrol of fungal plant pathogens using beneficial microorganisms is a safer alternative over synthetic fungicides. PHP12 is a bacterial strain isolated from healthy oil palm rhizosphere and is closely related to the recently described Burkholderia stagnalis, a member of the Burkholderia cepacia complex. This study aimed to characterize the antifungal activity spectrum of PHP12 and identify the antifungal compounds produced by the strain. Methodology and results: The antifungal activity of PHP12 was characterized by growing fungal strains in the presence and absence of PHP12 and measuring the radius of the antifungal zone. PHP12 inhibited the growth of fungal pathogens including Ganoderma boninense, Curvularia oryzae, Phellinus noxius and Colletotrichum capsici. However, PHP12 did not inhibit the growth of Trichoderma asperellum, a known fungal biocontrol agent. The antifungal compounds of PHP12 were precipitated using ammonium sulfate and further purified with HPLC followed by identification using Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometric (LC/ESI-MS). The LC/ESI-MS analysis showed the presence of an oligopeptide with a molecular weight of 1210.63 Da. The peptide consists of heavily modified amino acids that are linked by a hexose residue. Conclusion, significance and impact of study: Although characteristics of the antifungal compounds are similar to other antifungal peptides from Burkholderia such as occidiofungin, there have been no reports of antifungal peptides from B. stagnalis with the corresponding molecular weight or fragmentation profile. The novelty of the compound, as well as its antifungal spectrum, makes PHP12 an interesting strain to be investigated further as a biocontrol agent.