QUANTIFICATION OF POLYMER INTERACTIONS IN BACTERIAL ADHESION

Adhesion of bacteria to solids is governed by van der Waals, electrost atic, and acid-base (hydrophobic) interactions, which are combined in an extended DLVO model (DLVO-AB) and by interactions of bacterial surf ace polymers with the solid surfaces. A method to calculate polymer in teractions was not available yet, and their existence had been inferre d only qualitatively from the deviation of the actual adhesion from DL VO-AB-based expectations. Here, we present attempts (i) to quantify po lymer interactions from this deviation and (ii) to calculate them inde pendently as the sum of repulsive and attractive contributions. Repuls ion was assumed to result from the resistance of the polymer layer aga inst compression. Its calculation was most sensitive to the packing de nsity of the polymers in the cell envelope. Attraction was assumed to origin from polymer adsorption to the surface and was calculated on th e basis of adsorption data of isolated surface polymers. Comparison of total interaction energy curves with adhesion of six Gram-negative ba cteria to glass showed that the low adherence of five strains may have resulted from dominant polymer repulsion, i.e., hardly compressible c ell envelopes hindered the bacteria to approach the energy minima resu lting from DLVO-AB interactions. One strain adhered readily, possibly because polymer repulsion was low and polymer attraction and DLVO-AB f orces dominated the overall interaction.