E. coli Filaments Doing the Twist

Some bacteria in response to stress conditions, form extraordinarily long filaments with multiple chromosomes. It is the consequence of filamentation in which DNA duplication and cellular growth continues while cell division stops. Filamentation has been considered as a general survival strategy in repose to hostile environment. Here we further studied the motility of E. coli filaments treated by ciprofloxacin. We observed that despite different radii, different rotational frequency and different length varying from 4 microns to 50 microns, E. coli filaments retain constant swimming velocity of 20 microns per seconds as the normal 2 micron long E. coli mono-cell and do not tumble but only reversing their direction. Using high-speed confocal imaging, we show that these filaments are right-handed helices and move by rotating around the helix axis driven by a synchronous rotation of flagella along the entire filament and thus twisting through the media. The reversal motion of the filaments are accomplished by the synchronous reversal of the flagella. This swimming mechanism results a high diffusion coefficient due to very long velocity reversal persistence length enables bacterial filaments to leave the region of high stress quickly.