From soil to crop: a tiered screening strategy for lipopeptide-producing Bacillus with antifungal, antibacterial and plant growth-promoting activities

Introduction To address agrochemical pollution and improve microbial screening efficiency, this study aimed to develop an integrated pipeline for isolating high-yielding lipopeptide-producing Bacillus strains and validating their agricultural applications. Methods A tiered screening strategy combining hemolytic activity assay, plate confrontation, and oil-spreading assay was established to isolate strains from rhizosphere soils. Lipopeptide production was identified by MALDI-TOF MS and quantified via HPLC. Genomic analysis was performed to elucidate the genetic basis of lipopeptide synthesis. Crude lipopeptide extracts were evaluated for antimicrobial activity via plate assays, and for plant growth-promoting effects under pot and field conditions. Results The screening successfully identified potent Bacillus producers with multiple plant growth-promoting traits. Strain A1C-8 produced 1140.7 mg/L surfactin, Bv1 produced 450.1 mg/L iturin, and C5C-6 produced 707.8 mg/L fengycin. Crude extracts exhibited strong antimicrobial activity, with inhibition rates of 54.6% against Staphylococcus aureus and 273.3% against Rhizoctonia solani . Genomic analysis confirmed a robust genetic basis for lipopeptide synthesis. Notably, field trials demonstrated that lipopeptide extracts alone significantly enhanced crop growth: maize ear fresh weight increased by 32.46 % under 100 mg/L treatment, peanut pod number per plant rose by 42.75 % under 200 mg/L treatment, and sunflower fresh seed weight per capitulum improved by 35 % with 50 mg/L application. Discussion This study provides an integrated pipeline from strain screening to field validation, highlighting Bacillus lipopeptides as sustainable alternatives to agrochemicals for combined biocontrol and plant growth promotion.