title: Fluctuations and rheology in active bacterial suspensions.
abstract: We probe nonequilibrium properties of an active bacterial bath through measurements of correlations of passive tracer particles and the response function of a driven, optically trapped tracer. These measurements demonstrate violation of the fluctuation-dissipation theorem and enable us to extract the power spectrum of the active stress fluctuations. In some cases, we observe 1/sqrt[omega] scaling in the noise spectrum which we show can be derived from a theoretical model incorporating coupled stress, orientation, and concentration fluctuations of the bacteria.
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: D T N
authors.initials: DT
authors.lastname: Chen
authors.forename: A W C
authors.initials: AW
authors.lastname: Lau
authors.forename: L A
authors.initials: LA
authors.lastname: Hough
authors.forename: M F
authors.initials: MF
authors.lastname: Islam
authors.forename: M
authors.initials: M
authors.lastname: Goulian
authors.forename: T C
authors.initials: TC
authors.lastname: Lubensky
authors.forename: A G
authors.initials: AG
authors.lastname: Yodh
mesh_terms: D018929:Cell Culture Techniques; D004926:Escherichia coli / Q000502:physiology*; D012212:Rheology; D013269:Stochastic Processes; D013535:Suspensions; D014783:Viscosity
chemical_list: D013535:Suspensions