Sporulation suppression in Bacillus subtilis isolated from a Korean traditional fermented soybean modulates transcriptomic responses related to inflammation and oxidative stress in vitro models

Abstract

Bacillus subtilis is known for its probiotic and antioxidant potential. However, its functional properties at the molecular level remain underexplored. In this study, Bacillus subtilis isolated from Cheonggukjang, a Korean traditional fermented soybean paste (strain E5), was compared with its sporulation-deficient mutant (strain E5-M) obtained by disrupting the sigF gene and six consecutive downstream genes involved in sporulation (spoVAA, spoVAB, spoVAC, spoVAD, spoVAE, and spoVAF). Using RNA sequencing, we analyzed transcriptomic responses in human umbilical vein endothelial cell and hepatoblastoma cells pretreated with E5 or E5-M, followed by chemical induction of inflammation. Functional enrichment analysis revealed that E5 primarily regulated inflammatory pathways and intercellular signaling, while E5-M more prominently induced genes involved in tissue recovery, mitochondrial activity, and redox homeostasis. Real-time quantitative PCR validation confirmed a reduction in key inflammatory markers (tumor necrosis factor alpha, interleukin-1 beta, transcription factor p53, transcription factor p65 and BCL2-associated X protein), particularly in HepG2 cells. Whole genome sequencing showed no increase in allergenic potential due to the genetic modification. These findings suggest that suppression of sporulation in B. subtilis enhances its anti-inflammatory and oxidative stress-modulating activities, indicating its potential for safer and more functional applications in food and health industries.