Genetic and functional characterization of a Bacillus sp. strain excreting surfactin and antifungal metabolites partially identified as iturin-like compounds

Aims: A bacterial strain producing antifungal compounds active against the plant pathogenic fungi Fusarium, Rhizoctonia and Sclerotinia has been characterized and shown to control Rhizoctonia root rot of soya bean. Methods and Results: The metabolites excreted by Bacillus BNM 122 remained active after autoclaving, were resistant over a wide pH range and to hydrolytic enzymes. By 1H‐NMR and thin‐layer chromatography analyses surfactin and iturin‐like compounds were partially identified. Moreover, soya bean seeds bacterization with BNM 122 in a compost‐based formulation was as effective controlling Rhizoctonia solani as pentachloronitrobenzene. According to its 16S rDNA sequence BNM 122 was closely related to Bacillus amyloliquefaciens and Bacillus subtilis. PCR analysis of the 16S‐23S rRNA intergenic spacer region and repetitive sequence‐based PCR (rep‐PCR) genomic fingerprinting revealed a close genetic relationship to B. amyloliquefaciens. However, by physiological characterization using API tests, this strain resembled more B. subtilis. Conclusions: This is the first report describing the co‐production of surfactin and iturin‐like compounds by a putative strain of B. amyloliquefaciens. The synergistic effect of both lipopetides is a remarkable trait for a candidate biocontrol agent. Significance and Impact of the Study: This kind of research has relevance in order to minimize the use of synthetic fungicides and surfactants, contributing to the preservation of the environment.