On the relations between the elemental surface composition of yeasts and bacteria and their charge and hydrophobicity.

The elemental surface composition of eleven microorganisms was determined by X-ray photoelectron spectroscopy. Bacteria could be distinguished from yeasts by higher nitrogen and phosphate concentrations. Overall physico-chemical properties, electrical charge and hydrophobicity, were also investigated: the former by electrophoretic mobility measurements, the latter by contact angle and by hydrophobic interaction chromatography. Phosphate plays the major role in determining the surface electrostatic charge. A correlation is observed between the N/P atomic concentration ratio and the electrostatic charge. In bacteria, hydrophobicity is directly related to concentration of carbon in hydrocarbon form and inversely related to oxygen concentration or to the N/P ratio. For yeasts, a positive correlation is found between hydrophobicity and the N/P ratio, pointing at the role of proteins in determining the hydrophobicity.