Endogenous glycoside hydrolases reveal foraminiferal capacity to degrade terrestrial and marine polysaccharides.

Foraminifera, a major component of sediment biomass, play a critical role in sedimentary food webs. In this study, we identified and characterized endogenous glycoside hydrolases (GHs) in Cymbaloporetta bradyi, demonstrating their capacity to degrade both terrestrial and marine polysaccharides. Through transcriptomic and in silico analyses, prokaryotic, and eukaryotic contamination was minimized, ensuring the identified GHs were of foraminiferal origin. Our results revealed that cellulases, xylanases, chitinases, and mannanases are the most highly expressed GHs, even under nutrient-rich conditions. Pectinases, fucosidases, and laminarinases are also verified being possessed by C. bradyi. The presence of signal peptides in cellulases and cellulosome-related genes suggests an extracellular cellulose-degrading system in C. bradyi. These findings indicate that C. bradyi can metabolize polysaccharides from terrestrial plants and marine algae, reflecting adaptability to diverse sedimentary environments. As foraminifera are consumed by various deposit feeders and predators, the ability to degrade complex polysaccharides observed in C. bradyi may help explain their success in sedimentary environments. Although further studies on other foraminiferal species are necessary, having this metabolic capacity could make foraminifera important contributors to sedimentary food webs and the carbon cycle.