AGGLUTINATION OF THE CHLOROPHYCEAN FLAGELLATE DUNALIELLA TERTIOLECTA BY TREATMENT WITH LECTINS OR DIVALENT CATIONS AT ALKALINE pH1

Washed cells of Dunaliella tertiolecta Butcher became immobile and agglutinated upon exposure to 100–400 μ/mL lectins in NaCl solution. The agglutinations were strongest with Limulus polyphemus agglutinin and wheat‐germ agglutinin, moderate with soybean agglutinin and weakest with Concanavalin A. All lectin‐induced agglutinations were inhibited or mitigated by the simultaneous presence of specific lectin‐binding sugars. The differential sensitivity of the alga to these lectins suggested that sialic acid and/or N‐acetyl‐D‐glucosamine might be the predominant lectin‐receptor sugars in the algal surface coat, with N‐acetyl‐D‐galactosamine likely present as a lesser component. In the absence of lectins, the divalent cations Mg2+, Ca2+ or Mn2+ also caused agglutination, but this process required an alkaline pH of at least ca. 8.6–8.9. Such cation‐induced agglutination was reversibly inhibited by the cation complexing agent EDTA as well as by lowering the pH below 8.0. SEM observations of the agglutinations revealed random flagellar attachments as well as direct body contact between agglutinated cells.