The Role of Rhizobacterial Exopolysaccharides in Plant Growth Promotion and Abiotic Stress Resistance: A Review

Many microorganisms, including Plant Growth-Promoting Rhizobacteria (PGPR), are capable of synthesizing exopolysaccharides (EPS) and excreting them as either soluble or insoluble polymers. These EPS not only serve a crucial protective function, helping microorganisms survive abiotic stresses such as extreme temperatures, high salinity, and drought, but they also have significant potential in various biotechnological applications, particularly in agriculture. Incorporating EPS into low-input agricultural systems offers two major benefits: protecting the environment and enhancing sustainable crop production. EPS also improve soil structure, increase water retention, and boost nutrient availability, all of which are critical for maintaining healthy crops. This review aims to compile and critically assess the current literature on EPS, focusing on their chemical composition, classification, roles, biosynthesis, and methods of characterization. Additionally, the review examines how EPS positively affect plant growth under challenging environmental conditions such as high salinity, drought, temperature fluctuations, and heavy metal contamination. Finally, by highlighting the mechanisms through which PGPR and EPS enhance plant stress tolerance, this review underlines the broader implications of EPS in promoting more resilient agricultural systems capable of withstanding diverse environmental pressures. Keywords: Exopolysaccharides, PGPR, biosynthesis, temperature, salinity, drought, heavy metals, environmental resilience