Real-time movie of E. coli cells swimming in 10 micron wide, 1.5 micron high, poly(dimethylsiloxane) microchannels with soft, agar floors. The majority of cells are swimming on the right-hand side of the microchannel. [click above to view]
Researchers working together in the Howard Berg lab in MCB, the Rowland Institute at Harvard and the Whitesides lab in CCB have observed a new, interesting behavior of motile Escherichia coli cells: given the right prompting, the bacteria will “drive on the right.” When cells are confined in microchannels with floors made of a soft hydrogel, they preferentially swim closer to the gel floor, and along the right wall of the microchannel. The movement of cells in these channels resembles that of cars driving on a two-way street, unlike usual E. coli behavior. Cells are known to swim along surfaces in clockwise, circular trajectories, and in free solution, E. coli cells swim in random-walk trajectories.
E. coli cells can also cooperatively move over soft gel surfaces, a phenomenon called swarming. The authors examined E. coli swarmer cells moving in poly(dimethylsiloxane) (PDMS) channels with soft agar floors. It was found that bacterial cells move near a gel surface for much longer periods of time than a solid surface, a significant new insight into the interaction of bacterial cells with surfaces. Combined with the ability to “direct traffic” in new ways, these findings may allow new explorations of bacterial behavior in conditions more closely resembling pathogenic infection. In addition, controlling and guiding the motion of bacterial cells by using composite gel/PDMS microchannels may be useful in the development of cell-based microdevices such as biosensors.