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, chitinases, and mannanases are the most highly expressed GHs, even under nutrient-rich conditions. Xylanases, pectinases, and fucosidases 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 serve as prey for various deposit feeders and predators, their ability to degrade complex polysaccharides highlights their key role in sedimentary food webs and the carbon cycle. This study underscores the ecological significance of foraminifera in linking primary producers to higher trophic levels within marine sediments.