Roles of spoVF operon subunits A and B in regulating cell morphology and biofilm formation in the biocontrol agent Bacillus subtilis

Enhanced expression of spoVF operon (sporulation initiation factor; dipicolinic acid (DPA) synthase) in Bacillus subtilis vegetative cells has been reported to increase host attachment and biocontrol ability. However, how the spoVF operon regulates these essential biocontrol factors remains unknown. In this study, it was found that the knockout of the spoVFA or spoVFB subunits, individually ({Delta}A and{Delta} B), or together ({Delta}A{Delta}B), decreased DPA biosynthesis, host attachment, nutrient competition ability, and biocontrol efficacy in B. subtilis. Moreover, the cell shape of the knockout strains changed from short rod to spherical. qRT-PCR analysis indicated that the spoVF operon regulates TCA cycle expression and biofilm formation by balancing the amounts of various transcriptional factors, such as spo0A, SinR, and AbrB, and the cofactor NADPH. The regulatory mechanism of the spoVF operon in B. subtilis biofilm-related genes was proposed for the first time. IMPORTANCEBacillus subtilis SpoVF operon contains the spoVFA or spoVFB subunits, which are responsible for the dipicolinic acid synthase activity. Dipicolinic acid is an important component of B. subtilis spores. In this study, the roles of spoVFA or spoVFB subunits in the biocontrol ability B. subtilis were examined, indicating that the spoVFA subunit plays a key role in B. subtilis biofilm formation, cell morphology, growth, and nutrient competition ability. Additionally, the regulatory network connecting the spoVF operon with biofilm formation-related genes of B. subtilis was proposed. The results obtained in this study help to understand key genes involved in the biocontrol ability of B. subtilis.