A micro- and macro-scale analysis of the molecular details of bacterial adhesion to hydrophilic and hydrophobic surfaces.

摘要

Bacterial adhesion affects many fields from bioremediation to wastewater treatment. Since the adhesive properties of a bacterium are determined by its own surface structure and the surface it is coming in contact with, both of these variables must be investigated to understand adhesion. Bacterial infections are the leading cause of failure in medical implants such as catheters; bacterial biofilm formation can reduce the efficiency of wastewater treatment facilities, increase the drag on ship hulls, and increase the pressure drop across filtration membranes. Bacterial adhesion in aquifers can also reduce the effectiveness of bioaugmentation techniques for treating polluted landfills.; In this study, Microbe and Radiolabel Kinesis (MARK) mini-column tests and atomic force microscope (AFM) experiments were used to understand the dependence of bacterial adhesion characteristics on variables such as lipopolysaccharide (LPS) chain length, solution ionic strength, and substrate hydrophobicity. Column tests were also run using inorganic polystyrene colloids to demonstrate the influence of biomolecules, as well as colloid geometry, on adhesion.; It was shown that bacteria do adhere more readily to hydrophobic surfaces, as experiments of bacteria contacting silanized substrates showed. However, it was also shown that hydrophobicity is not the sole determinant of a bacterium's tendency to adhere. The molecular details, such as hydrocarbon chain length, can impact adhesion as well. Experiments with biomolecules showed that proteins (both Protein A and poly-D-lysine) chemically bound to colloids greatly increased their retention in a packed column. However, only a highly-positively charged protein (poly-D-lysine) had an impact on adhesion when merely physi-sorbed in the system. Dextran did not affect adhesion to either hydrophobic or hydrophilic surfaces when physi-sorbed. Column tests showed that rod-shaped colloids, which many bacteria can be considered to be, are retained more readily in a packed column than spherical colloids. AFM experiments were able to show marked differences in the approach curves between two Burkholderia cepacia strains. The strain that is less adhesive macroscopically showed repulsion upon approach, whereas the more adhesive strain showed an attraction. These findings will help contribute to the general understanding of bacterial adhesion and the molecular mechanisms responsible for it.