Bacterial deposition to fluoridated and non-fluoridated polyurethane coatings with different elastic modulus and surface tension in a parallel plate and a stagnation point flow chamber

Deposition of three marine bacterial strains with different cell surface hydrophobicities from artificial seawater to polyurethane coatings on glass with different surface tensions and elastic modulus was studied in situ in a parallel plate (PP) and stagnation point (SP) flow chamber. Different surface tensions of the coatings were established by changing the amount of fluorine, whereas using more or less branched polymers made different elastic moduli. Surface tensions of the coating, derived from measured contact angles with liquids, ranged from 11.9 to 44.9 mJ m^-2, while the elastic moduli, derived from force-distance curves as measured with an atomic force microscope were between 1.5 and 2.2 GPa. In both flow chambers, the most hydrophilic bacterium Halomonas pacifica adhered preferentially to the more hydrophilic, non-fluoridated coating, whereas the most hydrophobic bacterium Marinobacter hydrocarbonoclasticus showed a greater preference for the more hydrophobic coating. Bacterial adhesion in the PP flow chamber was not influenced by the elastic modulus of the coatings, but in the SP flow chamber bacteria adhered in higher numbers to hard surfaces than to coatings of lower elastic moduli.