Effect of Cations upon Hydrophobicity of Yeasts Grown in Amino Acid Media.

Hedrick, L. R. (Illinois Institute of Technology, Chicago), and C. J. Feren. Effect of cations upon hydrophobicity of yeasts grown in amino acid media. J. Bacteriol. 86:1288-1294. 1963.-Cells of four species of Hansenula, namely, H. holstii Y2154, H. subpelliculosa Y1683 and Y1542, and H. anomala Y365, were cultured for 3 days in a glucose-salts medium with one amino acid or (NH(4))(2)SO(4) as a nitrogen source. The l-amino acids used were glutamic acid, valine, proline, lysine, histidine, phenylalanine, tyrosine, and tryptophan. After growth, the cells were washed three times and added to small tubes which contained varying concentrations of chlorides of the cations Cs(+), K(+), Na(+), and Al(+++). The concentration of salt in ionic strength required for sedimenting yeast cells to form a fixed pellet represents an index of hydrophobicity of the cells, i.e., the smaller the ionic strength, the greater the hydrophobicity. All species grown in (NH(4))(2)SO(4) had a high degree of hydrophobicity. Cells of H. holstii and H. subpelliculosa Y1683 were very hydrophilic when cultured in the three aromatic amino acids as a nitrogen source and in proline as a carbon and a nitrogen source; cells of the latter species were much more hydrophobic if grown with proline as a nitrogen source. Cells of H. holstii cultured in l-glutamic acid as a nitrogen source were much more hydrophobic than those grown in proline as either a nitrogen or a carbon source. Cells of all species grown in l-lysine were more hydrophobic than cells cultured in the other amino acids tested. H. subpelliculosa Y1542 cells were somewhat more hydrophilic than those of H. anomala Y365, but both were much more hydrophobic than the other two yeasts studied. The concentration of cations required to detect an identical degree of hydrophobicity of cells decreased in the order Cs, Li, K, Na, and Al. This order corresponds to the compressibility method for estimating the water of hydration of the cations.