A Novel Aphis gossypii Killing Surfactin Produced by Bacillus australimaris TRM82479 of Taklamakan Desert Origin

The cotton aphid Aphis gossypii poses a global, serious threat to cotton yield and quality. Although chemical pesticides are effective, pollution and resistance are increasingly prominent, making development of new biopesticides a priority in the context of green agricultural development. Given that reports on the activity of surfactins against A. gossypii are limited, here, 107 Bacillus strains isolated from the extreme environment of the Chinese Taklamakan Desert were screened for insecticidal activity against A. gossypii using the leaf-dip method. Active strains were characterized by morphological observation, 16S rRNA gene sequencing, and phylogenetic analysis. Secondary metabolite synthesis genes were identified by whole-genome sequencing and antiSMASH analysis. B. australimaris strain TRM82479 showed 75.00% 48-h mortality against A. gossypii. An antiSMASH analysis showed that this strain has several gene clusters associated with the synthesis of nonribosomal peptide (NRP) fengycin and lichenysin lipopeptide analogs; therefore, we isolated and characterized its NRPs. A surfactin was the primary insecticidal substance, with an aqueous LC50 of 0.857 mg/mL and LC95 of 4.350 mg/mL. This study not only provides new strain resources for A. gossypii control, but also demonstrates the potential of surfactin as a biopesticide, which will lay a foundation for its future agricultural application.