The extracellular polymeric substances of desmids (Conjugatophyceae, Streptophyta): chemistry, structural analyses and implications in wetland biofilms

Abstract Desmids represent a group of advanced green algae that are commonly found in biofilm communities of freshwater wetlands. Desmids secrete significant amounts of extracellular polymeric substances (EPS) that form an extensive mucilaginous sheath external to the cell wall and function in adhesion, gliding-based movements and ultimate ensheathment within the biofilm complex. We have initiated biochemical and structural analyses of the EPS of desmids isolated from biofilms from the southeastern Adirondack region of New York including Penium cylindris, Penium spirostriolatum, Cosmarium sp. 1, Cosmarium sp. 2, Pleurotaenium trabecula, Tetmemorus brebissonii, Netrium digitus, Netrium oblongum, Netrium interruptum and Netrium interruptum 2509. Cosmarium sp. 1 EPS appeared as a homogeneous sheath that encapsulated the cells, whereas P. trabecula EPS occurred as dispersed patches, and N. oblongum EPS was reticulated and striated. Polysaccharides were the major component of the EPS (52–76%), and lectin label...