Patterns of Collective Bacterial Motion in Microfluidic Devices

O. Sipos, K. Nagy and P. Galajda

Abstract
We have studied active and passive forms of pattern formation and synchronized motion in high-density bacterial cell suspensions with phase contrast and epifluorescent videomicroscopy. We have shown that in high-density cultures of non-motile cells sedimentation patterns form. By comparing bacterial and colloidal suspensions we suggest that hydrodynamic interactions between sedimenting bacteria lead to patterns that one may consider a passive form of collective motion. Furthermore, we used microfluidic devices to investigate how solid boundaries influence the motion patterns of flagellated swimming bacteria in high-density cultures. We studied the emergence and dynamics of collective swimming of Escherichia coli. Using microfabricated chambers, we were able to control and stabilize the swimming patterns formed. Our results suggest that the physical features of the environment (solid boundaries and geometric constrictions) have strong effects on the swimming behavior and pattern formation of motile bacteria. Such effects may need to be considered when culturing bacteria in microchambers and microreactors.

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Keywords
synchronized motion, bacterial motility, collective behavior