title: Enhanced mixing and spatial instability in concentrated bacterial suspensions.
abstract: 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.
authors.affiliation: Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
authors.forename: Andrey
authors.initials: A
authors.lastname: Sokolov
authors.forename: Raymond E
authors.initials: RE
authors.lastname: Goldstein
authors.forename: Felix I
authors.initials: FI
authors.lastname: Feldchtein
authors.forename: Igor S
authors.initials: IS
authors.lastname: Aranson
mesh_terms: D001412:Bacillus subtilis / Q000166:cytology* / Q000378:metabolism; D009068:Movement; D013535:Suspensions; D041623:Tomography, Optical Coherence
chemical_list: D013535:Suspensions