Herein, Bacillus subtilis PBE-8's biocontrol efficacy was evaluated through physiological and metabolic approaches against Fusarium oxysporum f.sp. lycopersici (FOL). The study elaborates on PBE-8's cell-free filtrate (CFF) antifungal activity through mycelial growth inhibition, metabolite profiling, and substrates utilization patterns. Additionally, under different CFF concentrations, reduction in spore count (94%-55%), biomass (50%), and cytoplasmic bulbous protrusions in mycelia were also observed. Furthermore, the effect of bacterial CFF on FOL metabolism was confirmed through GC-MS. CFF suppresses the concentration of aliphatic amino acids like L-valine, L-leucine, L-Isoleucine, glycine, and fatty acids such as linoleic acid and α- linolenic acid during the co-culturing conditions, which are essential for pathogenicity and resistance against host's systemic acquired resistance. The phenotype microarray assay revealed that CFF-treated FOL shows phenotype loss in 507 (56.58%) out of 896 substrates. Among 507, twenty-seven substrates showed significant phenotype loss, among which four substrates such as L-glutamic acid, L-glutamine, ammonia, and L-arginine are common in different crucial metabolic pathways of FOL, like alanine, aspartate, and glutamate metabolism, arginine and proline, carbon metabolism, arginine biosynthesis, nitrogen metabolism, amino-acyl tRNA synthesis, and biosynthesis of amino acids. The results suggest that PBE-8 CFF has certain antifungal metabolites that hinder the fungal metabolic pathways.
Keywords: Bacillus subtilis PBE8; GC-MS analysis; fusarium oxysporum f.sp. lycopersici; metabolic pathways; phenotype microarray.
© The Author(s) 2022. Published by Oxford University Press on behalf of FEMS.