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.