Surface-properties of Microbial-cells and Their Role in Adhesion and Flocculation

(eng) X-ray photoelectron spectroscopy was used to investigate the chemical composition of the surface of yeasts and bacteria. The O/C, N/C and P/C atomic ratios, the proportion of various types of carbon (hydrocarbon, CO or CN and CO) and the proportion of oxygen engaged in hydroxide functions were measured. Phosphate is the determinant factor relevant to the surface potential, rather than nitrogen or carboxyl groups. Hydrophobicity in bacteria is directly related to the concentration of carbon in the hydrocarbon form and inversely related to oxygen concentration or to the N/P ratio; in yeasts it is directly related to the N/P ratio. The relevance of surface analysis to studies concerning microbial adhesion and (flocculation is discussed in view of the interplay of electrostatic properties and hydrophobicity in these processes.