title: Finite-size effects on bacterial population expansion under controlled flow conditions.
abstract: The expansion of biological species in natural environments is usually described as the combined effect of individual spatial dispersal and growth. In the case of aquatic ecosystems flow transport can also be extremely relevant as an extra, advection induced, dispersal factor. We designed and assembled a dedicated microfluidic device to control and quantify the expansion of populations of E. coli bacteria under both co-flowing and counter-flowing conditions, measuring the front speed at varying intensity of the imposed flow. At variance with respect to the case of classic advective-reactive-diffusive chemical fronts, we measure that almost irrespective of the counter-flow velocity, the front speed remains finite at a constant positive value. A simple model incorporating growth, dispersion and drift on finite-size hard beads allows to explain this finding as due to a finite volume effect of the bacteria. This indicates that models based on the Fisher-Kolmogorov-Petrovsky-Piscounov equation (FKPP) that ignore the finite size of organisms may be inaccurate to describe the physics of spatial growth dynamics of bacteria.
authors.affiliation: Department of Applied Physics and J.M. Burgers Centre for Fluid Dynamics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
authors.forename: Francesca
authors.initials: F
authors.lastname: Tesser
authors.affiliation: Department of Applied Physics and J.M. Burgers Centre for Fluid Dynamics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
authors.forename: Jos C H
authors.initials: JC
authors.lastname: Zeegers
authors.affiliation: Department of Applied Physics and J.M. Burgers Centre for Fluid Dynamics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
authors.forename: Herman J H
authors.initials: HJ
authors.lastname: Clercx
authors.affiliation: Department of Biomedical Engineering, Laboratory of Chemical Biology and Institute of Complex Molecular Systems, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
authors.forename: Luc
authors.initials: L
authors.lastname: Brunsveld
authors.affiliation: Department of Applied Physics and J.M. Burgers Centre for Fluid Dynamics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.|Department of Mathematics and Computer Science, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.|IAC-CNR, Via dei Taurini 19, 00185 Rome, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Toschi
mesh_terms: D004926:Escherichia coli / Q000254:growth & development*; D056656:Lab-On-A-Chip Devices; D008962:Models, Theoretical; D014871:Water Microbiology