Flocculation of Kluyveromyces marxianus is induced by a temperature upshift

An upshift of the growth temperature from 26 to 40 degrees C in the presence of calcium leads to the aggregation of Kluyveromyces marxianus cells and to the formation of flocs. Analysis of cell wall proteins, either by sodium dodecyl sulphate-polyacrylamide gel electrophoresis of extractable mannoproteins or by immunolocalization, revealed an accumulation of a protein with Mr 37 kDa(p37), upon flocculation. Immunological studies confirmed the homology of this protein with the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). When mRNA isolated from cells growing at 40 degrees C was translated in vitro, a 35 kDa newly labelled protein was synthesized and immunoprecipitation assays showed that this protein is recognized by p37-antiserum, suggesting that the 35 kDa polypeptide might be an unglycosylated precursor for of p37. The results indicated that the presence of this cell wall mannoprotein closely related to GAPDH is dependent on the growth temperature, suggesting its role as adhesin.