Comparison of the Antiadhesion Activity and Mechanism between Different Chiral Molecules L-Borneol and D-Borneol against Escherichia coli

The biofilm of Escherichia coli begins with a reversible adhesion phase, in which the movement of the planktonic bacteria could be regulated by a chemotaxis system. It has been reported that bacteria have adhesion differences with respect to different chiral configurations of borneols, but the underlying mechanism is unclear. Here, we explored the mechanisms by which L-borneol and D-borneol influenced the adhesion of E. coli mediated by chemoreceptors using real-time tracking of three-dimensional (3D) trajectories of bacterial motility and proteomics technology. We found that both borneols could restrain the adhesion and motility activity of E. coli. However, E. coli generated only escape movement toward the L-borneol. Both L-borneol and D-borneol had the foundation for binding to E. coli chemoreceptors Tar and Tsr, according to molecular docking analysis. E. coli lost this escape maneuver when Tar or Tsr was knocked out. Proteomics revealed that E. coli under D-borneol treatment exhibited a chemotaxis trend due to the upregulated proteins of chemotaxis and the flagellar assembly. However, insufficient ATP and proton motive force (PMF) in the D-borneol-treated group prevented E. coli from accomplishing the chemotactic behavior, resulting in reduced bacterial adhesion. In contrast, E. coli showed rapid repellent migration toward L-borneol in a short time by the 3D trajectory diagram. L-borneol prevented the adhesion of E. coli through the expulsion of chemotaxis. This study provides a theoretical basis and new thoughts for designing antibacterial adhesion strategies from the perspective of bacterial physiological regulation.