R Barak, D Mirelman, I Chet

The plant pathogen Sclerotium rolfsii produced a lectin in solid and liquid media. Extracts of the fungus, as well as a culture filtrate, agglutinated certain Gram-negative bacteria and yeasts, but not human red blood cells. d-Glucose, d-mannose (20 mM), and several of their derivatives specifically inhibited the agglutination of cells of Escherichia coli. Agglutination activity was also blocked by 1% trypsin or 1mM Na2-EDTA. The effect of the latter was reversed by the addition of Mn++ and CA++. Agglutinin activity was associated with the extracellular polysaccharide of S. rolfsii. The agglutinin was purified by ammonium sulfate precipitation, followed by gel filtration on a column of Sepharose 6B. SDS/polyacrylamide gel electrophoresis of the column-purified agglutinin showed two protein bands with molecular weights of 60 and 55 kdaltons. The ability of different isolates of the mycoparasite Trichoderma spp. to attack S. rolfsii was correlated with the agglutination of conidia of Trichoderma by S. rolfsii. The possible role of agglutinin in specific recognition in fungus-fungus interactions is discussed.