Genomic insights into biosurfactant-mediated antifungal activity of native Bacillus amyloliquefaciens EG6.1 against Fusarium oxysporum

Abstract

Abstract The soil-borne fungal pathogen Fusarium oxysporum is a major contributor to reduced agricultural productivity and degradation of agroecosystem health. Meanwhile, a molecular approach using microbial biocontrol agents offers a sustainable alternative to the use of chemical fungicides. This study aims to evaluate the potential of biosurfactant produced by Bacillus spp. in controlling Fusarium which integrated with Whole Genome Sequencing (WGS) analysis. Biosurfactant activity was screened using a hemolytic assay (qualitative), an emulsification assay and surface tension measurements (quantitative). Species identification was performed using 16S rRNA gene detection via the CTAB method. Antifungal activity was tested using swab and block methods with a completely randomized factorial design (3x3x3). The presence of biosurfactant biosynthesis gene clusters was detected using Whole Genome Sequencing (WGS) analysis. The results showed that isolates ES7.1, ESD1.6, and EG6.1 were identified as B. velezensis, B. cabrialesii, and B. amyloliquefaciens, with positive potential in producing biosurfactant compounds through indications of b-hemolysis in emulsification activity, a decrease in surface tension value > 20 mN/m, and the presence of an emulsion layer. Among the isolates, B. amyloliquefaciens EG6.1 showed the strongest antifungal activity against F. oxysporum, achieving 78% inhibition in both sonicated pellet and culture fractions. A complete genome analysis of B. amyloliquefaciens EG6.1 was performed the presence of non-ribosomal peptide synthetase (NRPS) gene clusters that encode the biosynthesis of surfactin, bacillomycin D, and fengisin, with significant potential to support antifungal activity. The presence of multiple biosynthesis clusters indicates the genetic capacity of strain EG6.1 to produce bioactive compounds with synergistic fungal inhibition mechanisms. Overall, these results confirm that B. amyloliquefaciens EG6.1, in its new formulation consisting of pellet fractions and sonicated culture, shows great potential as a green biocide and contributes to the development of disease management strategies, while supporting SDG’s 2 and 12.