A reference guide to microbial cell surface hydrophobicity based on contact angles

Abstract

Acid–base interactions form the origin of the hydrophobicity of microbial cell-surfaces and can be quantitated from contact angle measurements on microbial lawns with water, formamide, methyleneiodide and/or α-bromonaphthalene. This review provides a reference guide to microbial cell surface hydrophobicity based on contact angles with the above four diagnostic liquids and involves Acinetobacter calcoaceticus, Actinobacillus actinomycetemcomitans, actinomyces, Brevibacterium linens, various Candida species, Capnocytophaga gingivalis, Enterococci, Escherichia coli, lactobacilli, Leuconostoc mesenteroides, peptostreptococci, Porphyromonas gingivalis, Prevotella intermedia, pseudomonads, Serratia marcescens, staphylococci, and streptococci, adding up to a total of 142 isolates among which many ATCC and NCTC strains and two standard strains in hydrophobicity research. Comparison of the results of an acid-base analysis of the microbial cell surfaces on the basis of contact angles for the latter two strains and the results of the so-called MATH (microbial adhesion to hydrocarbons) assay for cell surface hydrophobicity, demonstrates that only contact angles can provide a real estimate of cell surface hydrophobicity. Furthermore, the compilation of contact angle data presented, makes clear that no generalizations concerning the physico-chemical surface properties of microorganisms may be made.