"Surface topography hinders bacterial surface motility"
Y-R Chang, ER Weeks, & WA Ducker, to be published in ACS Applied Materials & Interfaces

We demonstrate that the surface motility of the bacterium, Pseudomonas aeruginosa, is hindered by a crystalline hemispherical topography with wavelength in the range of 2-8 micron. The motility was determined by the analysis of time-lapse microscopy images of cells in a flowing growth medium maintained at 37 deg C. The net displacement of bacteria over 5 min is much lower on surfaces containing 2-8 micron hemispheres than on flat topography, but displacement on the 1 micron hemispheres is not lower. That is, there is a threshold between 1 and 2 micron for response to the topography. Cells on the 4 micron hemispheres were more likely to travel parallel to the local crystal axis than in other directions. Cells on the 8 micron topography were less likely to travel across the crowns of the hemispheres and were also more likely to make 30 deg - 50 deg turns than on flat surfaces. These results show that surface topography can act as a significant barrier to surface motility and may therefore hinder surface exploration by bacteria. Because surface exploration can be a part of the process whereby bacteria form colonies and seek nutrients, these results help to elucidate the mechanism by which surface topography hinders biofilm formation.