Impact of conditioning films on the initial adhesion of Burkholderia cepacia

Abstract

Bacterial initial adhesion to inertsurfaces in aquatic environments is mainly governed by the surface properties of the substratum, which can be altered significantly by the formation of conditioning films. Bacteria were tested for ability to adhere to bare glass slides and to slides coated with alginate, bovine serum albumin (BSA), or Suwannee River natural organic matter (SR-NOM). Three Burkholderia cepacia strains with different extracellular polymeric substance (EPS) secretion capacities were tested. The surface roughness of the slides was measured by atomic force microscopy (AFM), but its effect on bacterial initial adhesion was not significant. Our results showed the degree (number of cells per cm2) of initial adhesion among the three strains of B. cepacia was not significantly different, indicating that B. cepacia surface EPS did not impact adhesive capacity in the conditions tested. Depending on the conditioning film types and ionic strength conditions, conditioning film coatings can either enhance or reduce bacterial initial adhesion. Bacterial adhesion to bare slides and to alginate or SR-NOM coated slides increased with increasing ionic strength; however, a similar trend was not observed on BSA coated slides. Although BSA coated slides were the most hydrophobic and had the lowest negative surface charge among the surfaces tested, bacterial adhesion was not enhanced by the BSA coating. The extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was applied to explain bacterial adhesion to solid surfaces.