Roles of spoVF operon subunits A and B (dipicolinic acid synthase) in regulating cell morphology and biofilm formation in the biocontrol agent Bacillus subtilis

BACKGROUND The spoVF operon, encoding the dipicolinic acid (DPA) synthase, is critical for sporulation in Bacillus subtilis . A recent study suggested that spoVF expression in vegetative cells promotes biofilm formation, yet the detailed regulatory pathways and the underlying metabolic connections remain to be fully elucidated. RESULTS In this study, deletion of spoVF subunits spoVFA and spoVFB severely reduced DPA synthesis, downregulated mreB gene expression, and impaired biofilm formation, with mutant ΔA showing stronger effects than mutant ΔB. Although wild type B. subtilis 168 cells exhibited rod shape, double mutant ΔAΔB cells were spherical. In the MT strain, engineered for enhanced spoVF expression during vegetative growth, the upregulation of key TCA cycle genes (e.g., citC ) and glutamate synthesis genes (e.g., gltA ) was observed. This metabolic reprogramming was accompanied by the promotion of Spo0A phosphorylation. The activated Spo0A~P then inhibited the SinR and AbrB repressors, which led to the activation of the eps and tasA biofilm operons. The MT strain showed superior stress tolerance to high temperature (42 °C), salt, acidic and alkaline pH, and UV-A and UV-B radiation. Additionally, the MT strain exhibited higher nutrient competition ability, and in vitro and in vivo antifungal activities against the sweet potato ( Ipomoea batatas L. Lam) storage root pathogen Ceratocystis fimbriata compared to mutant ΔA, ΔB, and ΔAΔB strains. CONCLUSIONS This study elucidates how the spoVF operon links the central metabolic pathways with B. subtilis cell morphology and biofilm formation, offering a novel target for engineering advanced Bacillus -based biocontrol agents. © 2026 Society of Chemical Industry.