CONTROL OF PARTITIONING OF BACTERIAL-CELLS AND CHARACTERIZATION OF THEIR SURFACE-PROPERTIES IN AQUEOUS 2-PHASE SYSTEMS

A systematic approach to the characterization of the physicochemical p roperties of bacterial cell surfaces (isoelectric point, surface net a nd local hydrophobicity) has been presented using the same aqueous two -phase partitioning method that was applied for the characterization o f protein surfaces (Kuboi et al., Solv. Extr. Res. Dev, Japan, 1, 42-5 2, 1995). It was found that the isoelectric point (pI) could be determ ined by cross partition method and that the pI of Escherichia coli cel ls is generally low. At the pI, the surface hydrophobicity (HFS) of th e bacterial cells was determined by using the slope of the relationshi p between the hydrophobic differences of the two phases and the partit ion coefficient of the bacterial cells. The partition behavior of cell s was found to be influenced by the addition of relatively low concent ration of salts. The addition of nonionic surfactants of the Triton X- series led to an increase in the partitioning of the cells (Delta ln K -Cell) by causing a hydrophobic interaction between Triton molecules a nd the cell surface. This effect is probably due to the interaction be tween the hydrophobic groups of the surfactant and the local hydrophob ic binding sites of the cell surface, such as the membrane proteins an d phospholipid membranes. By using these parameters, such as the pI, H FS, and bin K-Cell the surface properties of bacterial cells which wer e exposed by heat treatment mere analyzed.