Metabolomic Profiling and Genome-Wide Analysis of Bacillus subtilis NBAIR-BSWG1 Reveals Cyclic Lipopeptides as Key Antagonists

Understanding bacterial genetics and metabolism is vital for developing biopesticides. This study investigates Bacillus subtilis NBAIR-BSWG1, a strain well known for its antagonistic potential. Crude lipopeptides extracted from the strain were evaluated for in vitro activity, showing complete inhibition of Rhizoctonia solani at a concentration of 50 μL/mL potato dextrose agar. To delve deeper into its antagonistic mechanisms, we conducted whole-genome sequencing of NBAIR-BSWG1 using Illumina NextSeq 500. Subsequent analysis with the BlastX diamond tool revealed 19 key biosurfactant genes, including surfactin (srfAA, srfAC, srfAD, srfP), fengycin (ppsE, ppsD, ppsC, ppsB), and putisolvin (dnaK), which were further confirmed by PCR using specific primers. Meanwhile, antiSMASH analysis revealed gene clusters with 100% similarity to those responsible for the synthesis of fengycin, bacilaene, bacillibactin, subtilosin A, and bacilysin, as well as clusters with 82% similarity to surfactin synthesis genes. Additionally, liquid chromatography-mass spectrometry was performed to analyze the cell-free extract produced by NBAIR-BSWG1, revealing the presence of various cyclic lipopeptides, including multiple peaks corresponding to surfactin, iturin, and several novel lipopeptide compounds. This study highlights B. subtilis NBAIR-BSWG1 cyclic lipopeptides as a key to broad-spectrum bio-control and establishes the strain as highly potent.