The Mechanisms of Bacillus subtilis as a Plant-Beneficial Rhizobacterium in Plant-Microbe Interactions

The rhizosphere is a dynamic microenvironment where plants interact with diverse native microbial communities that significantly influence growth, health, and resilience. Among plant-growth-promoting rhizobacteria, Bacillus subtilis stands out as a multifunctional species with exceptional ability to colonize plant roots, form robust biofilm, and confer protection against diseases. Its resilience as a spore-former, genetic ability to produce active compounds such as antibiotics, and phytohormones make it a valuable species for agriculture and forest sustainability. This review reveals the molecular and physiological mechanisms underlying B. subtilis interactions with plants, focusing on biofilm formation, root colonization, biocontrol and disease suppression, and promotion of plant growth. We further examine its role in root colonization, which triggers extensive reprogramming of plant gene expression, thereby integrating growth promotion with enhanced immune competence through a network that regulates plant-beneficial traits. Its genomic regulation supports colonization, stress tolerance, and immune support, while synergistic interactions with other microbes highlight its adaptability. As a versatile bio-fertilizer and biocontrol agent, further study of its strain-specific traits and rhizosphere interactions is key to maximizing its role in sustainable agriculture and forest control under environmental changes.