Immunogold-labeling analysis of alginate distributions in the cell walls of chromophyte algae

The immunogold electron microscopy technique was employed to detect the presence of alginates in the cell walls of selected chromophyte species. Anti-alginate antiserum labeled the cell walls of Sphacelaria and Scytosiphon (Phaeophyceae), Tribonema, Vaucheria, Botrydium, Botrydiopsis (Xanthophyceae) and an‘un-described filamentous species’ (incertae cedis), but it did not label those of Giraudyopsis, Phaeosaccion (Chrysomeridales), Antithamnion (Rhodophyceae) and Bryopsis (Ulvophyceae). This is the first report of the occurrence of alginates in the chromophyte outside Phaeophyceae. The absence of alginates in Chrysomeridales, which has an unclear phylogenetic position, implies a rather distant phylogenetic relationship of the order Chrysomeridales from Phaeophyceae/Xanthophyceae.