Adhesion of bacteria to solids is governed by van der Waals, electrostatic, and acid-base (hydrophobic) interactions, which are combined in an extended DLVO model (DLVO-AB) and by interactions of bacterial surface polymers with the solid surfaces. A method to calculate polymer interactions was not available yet, and their existence had been inferred only qualitatively from the deviation of the actual adhesion from DLVO-AB-based expectations. Here, we present attempts (i) to quantify polymer interactions from this deviation and (ii) to calculate them independently as the sum of repulsive and attractive contributions. Repulsion was assumed to result from the resistance of the polymer layer against compression. Its calculation was most sensitive to the packing density of the polymers in the cell envelope. Attraction was assumed to origin from polymer adsorption to the surface and was calculated on the basis of adsorption data of isolated surface polymers. Comparison of total interaction energy curves with adhesion of six Gram-negative bacteria to glass showed that the low adherence of five strains may have resulted from dominant polymer repulsion, i.e., hardly compressible cell envelopes hindered the bacteria to approach the energy minima resulting from DLVO-AB interactions. One strain adhered readily, possibly because polymer repulsion was low and polymer attraction and DLVO-AB forces dominated the overall interaction.

During the production of the pesticide lindane (γ-hexachlorocyclohexane; γ-HCH), large quantities of byproducts, like the α-, β-, and δ-HCH isomers, were discarded at dump sites. β-HCH was found to be extremely persistent in the environment under aerobic conditions. We studied the degradation of this isomer under methanogenic conditions in a flow-through column packed with polluted sediment. β-HCH was completely removed in this system. Chlorobenzene was detected in the effluent as a product. A β-HCH transforming anaerobic enrichment culture was obtained in batch cultures by using the column material as inoculum. δ-2,3,4,5-Tetrachlorocyclohexene is proposed as an intermediate during transformation, while benzene and chlorobenzene were formed as stable end products. The enrichment culture was also able to dechlorinate α-HCH at a comparable rate and γ- and δ-HCH at lower rates. Dechlorination was inhibited by the addition of vancomycin, but not by the addition of bromoethanesulfonic acid. Pasteurization inhibited dechlorination completely. This is the first detailed description of the biodegradation of β-HCH, including intermediate and end product identification, under defined anaerobic conditions.