The role of quorum sensing effector ComA in regulating biofilm formation and surfactin production in Bacillus subtilis ASAG 010

Bacillus species are valuable agents in biocontrol and sustainable agriculture. This study focuses on the properties of Bacillus subtilis ASAG 010, a strain isolated from wheat-associated soil, which exhibited potent antifungal activity against multiple plant pathogens, including Fusarium graminearum. The strain effectively controlled Fusarium head blight in wheat and demonstrated the ability to degrade the mycotoxin zearalenone (ZEN). High-performance liquid chromatography (HPLC) and MALDI-TOF-MS analyses, coupled with genetic verification, identified surfactin as the primary antifungal compound produced by B. subtilis ASAG 010. Analysis of the static fermentation process revealed that a mature biofilm structure significantly enhanced surfactin synthesis in B. subtilis ASAG 010. To investigate the interplay between quorum sensing (QS), biofilm formation, and surfactin production, a ComA-deficient mutant was constructed. The mutant exhibited reduced extracellular polysaccharides, proteins, and γ-PGA – key biofilm matrix components – and lower expression of EpsA and BlsA. HPLC analysis showed a significantly reduced in surfactin production, and DNA pull-down assays confirmed that ComA directly binds upstream of the srfA gene, which encodes surfactin biosynthesis. These findings establish ComA as a key regulator of biofilm integrity and surfactin production, providing insights into the biocontrol potential of B. subtilis ASAG 010 for food safety and agricultural sustainability.