The adhesion of three microorganisms (Saccharomyces cerevisiae, Acetobacter aceti, and Moniliella pollinis) to different materials has been studied using various supports (glass, metals, plastics), some of which were treated by an Fe(III) solution. The surface properties of the cells were characterized by the zeta potential and an index of hydrophobicity; characterization of the supports involved surface chemical analysis (XPS) and contact angle measurements. Cell suspensions in pure water at a given pH were left to settle on plates; the latter were then rinsed and examined microscopically, Saccharomyces cerevisiae and A. aceti adhere to metals under certain pH conditions but do not adhere to any of the other materials tested unless it is previously treated by ferric ions; adhesion of these hydrophilic cells is essentially controlled by electrostatic interactions. Moniliella pollinis adhere spontaneously to glass and to polymeric materials, but its attachment is also influenced by cell-cell or cell-support electrostatic repulsions; near the cell isoelectric point, cell flocculation is competing with adhesion to a support.

A collection of microorganisms, including a microfungus and various yeasts and bacteria has been analyzed by X‐ray photoelectron spectroscopy (XPS). A correlation is observed between the N/P atomic concentration ratio of the cell surface and the cell electrophoretic mobility measured at pH 4, indicating that the dehydrated surface analyzed by XPS is representative of the cell surface in contact with water. Deprotonation of phosphate groups plays a predominant role in the development of the cell negative charge, and carboxylic groups are not involved appreciably; a partial neutralization is allowed by protonation of free amino groups of proteins. These results advocate a broader use of XPS in order to understand physicochemical properties (electrostatic charge, hydrophobicity, ion binding) of the surface of cells, which are of prime importance in various processes occurring in nature and technology.

The attachment of three strains of Acetobacter aceti (ATCC 23747, ATCC 23748, NCIB 8246), with or without capsule, cultured under different conditions has been investigated in solutions of controlled pH. Various materials (silicates, organic polymers) have been used as supports, and the results have been related to the surface properties of the cells and supports. Cells that do not have a capsule do not adhere to the tested materials, whatever their hydrophobicity, unless the latter are previously treated by ferric ions to make their surface less negative. Cells that possess a capsule adhere to non-treated supports. In all cases the highest density of the adhering cellular film is obtained when the electrostatic repulsions between a cell and the support and between cells are reduced (surface charge of the support less negative, lower pH). The capsule influences adhesion by affecting the interplay between electrostatic interactions and hydrophobic bonding; moreover, capsule polymers may favor adhesion by acting as binding agent. The occurrence of cell flocculation gives rise to greater heterogeneity and lower cell density in the film of adhering cells.