Adhesion of the marine bacterium Pseudomonas sp. NCIMB 2021 to different hydrogel surfaces

Adhesion of Pseudomonas sp. NCIMB 2021 was tested on different non-solid hydrogel surfaces under different shear conditions. Gels consisting of alginate (highly anionic), chitosan (highly cationic), modified polyvinyl alcohol PVA-SbQ (very low cationic) and agarose (neutral) were casted in moulds custom-made for a rotating annular biofilm reactor. Cells were stained with SYBRR Green I nucleic acid gel stain, and images were collected using a confocal laser scanning microscope. Relative adhesion was quantified by determining percent cell coverage using image analysis. Bacterial adhesion on gels decreased at higher shear rates. At low shear rates, adhesion varied significantly between different gels, in the following descending order: alginate > agarose > chitosan > PVA-SbQ. Only adhesion to alginate remained significantly higher than to the others at high shear rates. Lowest cell coverage at all shear rates was recorded on PVA-SbQ gels. Clearly, the macroscopic hydrophobicity of the hydrogel surfaces did not enhance adhesion as observed for solid surfaces. A 5% PVA-SbQ gel showed the most promising antifouling properties.