Reversible depletion-driven capture of bacterial cells on non-adhesive surfaces

The adhesion of bacteria on surfaces is critical in processes such as biofouling, biofilm formation, and the infection of plants and animals. Bacteria-surface interactions involving hydrodynamics and physicochemical forces (i.e. van der Waals and electrostatic) has been well studied. However, no study has discussed the role of depletion force in bacteria adhesion to surface, even though bacteria are often found in polymer rich environments where polymer-driven depletion produces attractions. Here, we demonstrate how non-motile Escherichia coli (E. coli) are captured on polyethylene glycol (PEG) brush surfaces which are non-adhesive to E. coli on their own. The capture is reversible, and the cells are released with the removal of the polymer solution and hence the depletion force. PEG of two different molecular weights were used as depletants. We also studied the influence of depletion driven aggregation on cell capturing. The depletion driven aggregation and depletion driven surface capture are two competing mechanism in this system.