Endospore-producing Endophytes: Structural Adaptations, Functional Roles, and Their Significance in Plant Growth and Stress Management
M. S. Nandana
*
Department of Microbiology, College of Agriculture, Kerala Agricultural University, Vellayani, Thiruvananthapuram, 695 522, Kerala, India.
K. N. Anith
Department of Microbiology, College of Agriculture, Kerala Agricultural University, Vellayani, Thiruvananthapuram, 695 522, Kerala, India.
*Author to whom correspondence should be addressed.
Abstract
The primary genera of endospore-producing endophytes are Bacillus and Clostridium, both known for their robust survival strategies and diverse metabolic capabilities. Endospore-forming endophytic bacteria, particularly members of the genus Bacillus, are gaining increasing recognition for their multifaceted roles in sustainable agriculture. These microorganisms are capable of colonizing internal plant tissues and forming highly resistant endospores that ensure their survival under harsh environmental conditions. This review highlights the structural and functional aspects of bacterial endospores, including their formation, layers, and resistance mechanisms. Furthermore, it explores the significance of endophytic Bacillus spp. as plant growth-promoting agents through nutrient solubilization, phytohormone production, and disease suppression. The ability of these bacteria to alleviate biotic stresses through antimicrobial metabolites and systemic resistance, as well as their contribution to abiotic stress tolerance via antioxidant enzyme activation and ion homeostasis, is discussed in detail. The unique combination of persistence, adaptability, and beneficial plant interactions makes endospore-forming Bacillus spp. highly valuable for modern agricultural applications, especially under changing climatic conditions.
Keywords: Bacillus, endospore, endophytes, Plant Growth-Promoting Bacteria (PGPB), abiotic stress, biocontrol, ISR, nutrient solubilization, drought tolerance, salinity stress