基因组导向的ser和shlB基因解析揭示了海洋链球菌PXG6在菜青虫体内多因素致病机制

Abstract

The rapid evolution of pesticide resistance in Plutella xylostella has reduced the effectiveness of conventional pest control methods in cruciferous crops. This study investigated the virulence of Serratia marcescens PXG6 against P. xylostella and identified two putative virulence factors, ser (serralysin) and shlB (hemolysin transporter). Whole-genome sequencing revealed a GC content of 59.65%, 4650 predicted genes, multiple secretion systems (types I, V, and VI), and 715 putative virulence-related genes. Bioinformatic analyses predicted type IV pili, serralysin, hemolysin, and flagella as pathogenic determinants. Purified prodigiosin exhibited concentration-dependent insecticidal activity, whereas bacterial proteins alone caused little larval mortality, indicating that full virulence depends on live bacterial cells. Gene knockout mutants Δ ser and Δ shlB exhibited altered growth, motility, biofilm formation, and stress tolerance. Deletion of shlB significantly reduced hemolytic activity, protein secretion, and virulence against P. xylostella , whereas Δ ser had minimal impact on larval survival. Overall, PXG6 pathogenicity involves multiple bacterial components, with shlB playing a key role in virulence. These findings improve our understanding of the pathogenic mechanisms of PXG6 and support the development of S. marcescens -based biocontrol strategies against P. xylostella . Graphical In this study, we investigated the pathogenic mechanisms of an entomopathogenic Serratia marcescens strain (PXG6) isolated from Plutella xylostella , a globally destructive pest of cruciferous crops. Using an integrated approach combining whole-genome sequencing, bioinformatic virulence prediction, targeted gene knockout, and insect bioassays, we demonstrate that PXG6 pathogenicity is a multifactorial, cell-associated process rather than being driven by secreted metabolites alone.