RANDOM MOTILITY OF SWIMMING BACTERIA IN RESTRICTED GEOMETRIES

The effects of restricted geometries on the swimming behavior of Esche richia coli were examined. Videomicroscopy and image analysis techniqu es were used to measure single-cell motility parameters (cell velocity , tumbling probability, and turn angle) in microfabricated 2-D channel s ranging from 2 to 20 mu m in height. Macroscopic motility coefficien ts were calculated from the single-cell data and compared to literatur e values. These observations indicate that single-cell parameters rema in nearly constant in confined spaces in which channel heights approac h the size of the bacterium. The nearly constant swimming behavior of individual cells in confined geometries indicates that the macroscopic motility coefficient describing population behavior will be greater t han the unrestricted value by a factor proportional to the dimensional ity of the system.