FLOCCULATION OF THE YEAST CANDIDA-FAMATA (DEBARYOMYCES-HANSENII) - ANESSENTIAL ROLE FOR PEPTONE

Aggregation of Candida famata (Debaryomyces hansenii) is consistent wi th being a form of lectin-mediated yeast flocculation. Flocculation of C, famata is unusual in that it requires the presence of peptone, eit her in the growth medium or added later to harvested cells in buffer. Flocculation after pep:one addition was rapid, being largely complete within 10 min. Heat-killed cells also flocculated, arguing for direct participation of peptone in the flocculation binding mechanism. Floccu lent C. famata cells progressively lost the ability to flocculate when washed with EDTA. Flocculation was fully restored by peptone addition ; calcium addition was without effect. C. famata cells were able to ag glutinate erythrocytes in the presence or absence of peptone. Pronase E-treated yeast lost both the ability to haemagglutinate and self-floc culate. Haemagglutination was not diminished by progressive EDTA washi ng, suggesting that surface lectins remained present and active on the yeast cell walls. Non-flocculating C. famata cells mutually flocculat ed with non-flocculent Schizosaccharomyces cells, shown to have surfac e-exposed galactose residues. Mutual flocculation was lost following t reatment of C. famata with Pronase E. It was concluded that the cell w all of C. famata contains lectins enabling haemagglutination and mutua l flocculation but lacks carbohydrate receptors for these lectins. Thi s yeast self-flocculates only via bridging multi-valent carbohydrates; these being present in peptone.