Microbial exopolysaccharide production by polyextremophiles in the adaptation to multiple extremes

Over the past few decades, research on polyextremophiles has revealed a diverse range of organisms adapted to multiple extreme conditions, such as combinations of high and low temperatures, acidity, pressure, salinity, and radiation. Under multiple extremes, a key survival mechanism is the production of exopolysaccharides (EPSs) via cell wall-associated or extracellular glycosyltransferases (GTs). EPSs not only protect cells against environmental extremes, desiccation, phage attacks, phagocytosis, and antibiotics; they also play important roles in inter- and intra-microbial interactions, quorum sensing, virulence, energy storage, and biofilm formation. Despite extensive studies on EPSs from extremophiles, knowledge on EPS production in polyextremophiles remains limited, particularly for psychrophiles, halophiles, and piezophiles. This review focuses on the adaptive strategies of polyextremophiles under multiple stress conditions, emphasizing the functional significance of EPS production. By providing an integrated perspective on polyextremophiles and their survival mechanisms, this work highlights the critical role of EPSs in their adaptation to extreme habitats and their potential biotechnological applications.