KLUYVEROMYCES-MARXIANUS FLOCCULENCE AND GROWTH AT HIGH-TEMPERATURE ISDEPENDENT ON THE PRESENCE OF THE PROTEIN P37

A Kluyveromyces marxianus mutant deficient in p37, a glyceraldehyde-3- phosphate dehydrogenase (GAPDH)-like protein, was obtained and charact erized with respect to flocculation behaviour, resistance to temperatu res above the optimum for growth, morphology, growth, calcofluor white sensitivity and GAPDH activity. In YPD media, the mutant cells were u nable to flocculate and were thermosensitive. However, this thermosens itivity could be overcome by the presence of calcium. Calcofluor white was toxic to the mutant, indicating that the mutation affects cell wa ll structure. The contribution of p37 to total GAPDH activity was 25% when cells were using glucose as carbon source and 50% when cells were growing in 3% ethanol. These results indicate that p37 is likely to b e involved in thermotolerance and flocculation, which can be related t o its contribution to cell wall integrity.