Gas chromatography-mass spectrometry comparative analysis of secondary metabolites produced by some Bacillus spp. as biocontrol agents against phytopathogenic fungi

Abstract

The widespread use of chemical fungicides is a current health and environmental concern. Hence, the quest for novel eco-friendly biocontrol agents poses a forthcoming challenge. In this study, 21 rhizosphere Bacillus isolates were isolated and assessed for their ability to inhibit Rhizoctonia solani growth. The four isolates (KSAR3, KSAR7, KSAR10, and KSAR11) demonstrated antagonistic activity, with the KSAR7 isolate displaying the greatest growth inhibition (55%). By sequencing the 16S rRNA gene, the four isolates were found to be B. subtilis (KSAR3 and KSAR10), B. licheniformis (KSAR11), and B. tequilensis (KSAR7). Using gas chromatography-mass spectrometry analysis, the chemical characterization and identification of the generated bacterial bioactive secondary metabolite were carried out. A total of 29 biologically active aliphatic and aromatic compounds were identified, among which bis(2-ethylhexyl) phthalate, dotriacontane, docosane, hexadecanoic acid, and octadecanoic acid were produced by the four Bacillus isolates. Additionally, seven distinct chemicals, including benzene, 1,3,5-trimethyl, were exclusively produced by the KSAR7 isolate. This may elucidate why it is more efficacious in suppressing R. solani. Ultimately, the results showed that B. tequilensis could be a good source of natural biocontrol antifungal agents for agriculture and food security, providing an alternative to synthetic pesticides.