EXTRACELLULAR-MATRIX ASSEMBLY IN DIATOMS (BACILLARIOPHYCEAE) .1. A MODEL OF ADHESIVES BASED ON CHEMICAL CHARACTERIZATION AND LOCALIZATION OF POLYSACCHARIDES FROM THE MARINE DIATOM ACHNANTHES LONGIPES AND OTHERDIATOMS

Extracellular adhesives from the diatoms Achnanthes longipes, Amphora coffeaeformis, Cymbella cistula, and Cymbella mexicana were characteri zed by monosaccharide and methylation analysis, lectin-fluorescein iso thiocyanate localization, and cytochemical staining. Polysaccharide wa s the major component of adhesives formed during cell motility, synthe sis of a basal pad, and/or production of a highly organized shaft. Hot water-insoluble/hot 0.5 M NaHCO3-soluble anionic polysaccharides from A. longipes and A. coffeaeformis adhesives were primarily composed of galactosyl (64-70%) and fucosyl (32-42%) residues. In A. longipes pol ymers, 2,3-, t-, 3-, and 4-linked/substituted galactosyl, t-, 3-, 4-, and 2-linked fucosyl, and t- and 2-linked glucuronic acid residues pre dominated. Adhesive polysaccharides from C. cistula were EDTA-soluble, sulfated, consisted of 83% galactosyl (4-, 4,6-, and 3,4-linked/subst ituted) and 13% xylosyl (t-, 4(f)/5(p)-, and 3(p)-linked/substituted) residues, and contained no uronosyl residues. Ulex europaeus agglutini n uniformly localized alpha(1,2)-L-fucose units in C. cistula and Achn anthes adhesives formed during motility and in the pads of A. longipes . D-Galactose residues were localized throughout the shafts of C. cist ula and capsules of A. coffeaeformis. D-Mannose and/or D-glucose, D-ga lactose, and alpha(t)-L-fucose residues were uniformly localized in th e outer layers of A. longipes shafts by Cancavalia ensiformis, Abrus p recatorius, and Lotos tetragonolobus agglutinin, respectively. A model for diatom cell adhesive structure was developed from chemical charac terization, localization, and microscopic observation of extracellular adhesive components formed during the diatom cell-attachment process.