Enhanced mixing and spatial instability in concentrated bacterial suspensions.
High-resolution optical coherence tomography is used to study the onset of a large-scale convective motion in free-standing thin films of adjustable thickness containing suspensions of swimming aerobic bacteria. Clear evidence is found that beyond a threshold film thickness there exists a transition from quasi-two-dimensional collective swimming to three-dimensional turbulent behavior. The latter state, qualitatively different from bioconvection in dilute bacterial suspensions, is characterized by enhanced diffusivities of oxygen and bacteria. These results emphasize the impact of self-organized bacterial locomotion on the onset of three-dimensional dynamics, and suggest key ingredients necessary to extend standard models of bioconvection to incorporate effects of large-scale collective motion.
Sokolov
Andrey
A
Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
Goldstein
Raymond E
RE
Feldchtein
Felix I
FI
Aranson
Igor S
IS
D001412:Bacillus subtilis / Q000166:cytology* / Q000378:metabolism; D009068:Movement; D013535:Suspensions; D041623:Tomography, Optical Coherence
D013535:Suspensions