The atomic force microscope (AFM) was used to directly measure the forces of interaction between E. coli D21 bacteria and hydrophilic glass or hydrophobic N-octadecyltrichlorosilane (OTS)-treated glass substrates coated with the block copolymers, poly(ethylene glycol) (PEG)-lysine dendron or Pluronic F127 surfactant, respectively. Short-range repulsive interactions between bacterial cells and substrates coated with the block copolymers were detected by the AFM over distances of separation comparable to the extended length of the PEG polymer chains. In contrast, glass and OTS-treated glass devoid of PEG-lysine dendron or Pluronic F127 exerted long-range attractive forces on E. coli D21 bacteria. Thus, polymeric brush layers appear to not only block the long-range attractive forces of interaction between bacteria and substrates but also introduce repulsive steric effects.