title: Failed escape: solid surfaces prevent tumbling of Escherichia coli.
abstract: Understanding how bacteria move close to surfaces is crucial for a broad range of microbial processes including biofilm formation, bacterial dispersion, and pathogenic infections. We used digital holographic microscopy to capture a large number (>10(3)) of three-dimensional Escherichia coli trajectories near and far from a surface. We found that within 20  μm from a surface tumbles are suppressed by 50% and reorientations are largely confined to surface-parallel directions, preventing escape of bacteria from the near-surface region. A hydrodynamic model indicates that the tumble suppression is likely due to a surface-induced reduction in the hydrodynamic force responsible for the flagellar unbundling that causes tumbling. These findings imply that tumbling does not provide an effective means to escape trapping near surfaces.
authors.affiliation: Mechanical Engineering Department, Texas Tech University, 2703 7th Street, Lubbock, Texas 79409, USA.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Molaei
authors.affiliation: Ralph M. Parsons Laboratory, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 15 Vassar Street, Cambridge, Massachusetts 02139, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Barry
authors.affiliation: Ralph M. Parsons Laboratory, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 15 Vassar Street, Cambridge, Massachusetts 02139, USA.
authors.forename: Roman
authors.initials: R
authors.lastname: Stocker
authors.affiliation: Mechanical Engineering Department, Texas Tech University, 2703 7th Street, Lubbock, Texas 79409, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Sheng
mesh_terms: D004926:Escherichia coli / Q000502:physiology*; D057446:Hydrodynamics; D008954:Models, Biological; D009068:Movement; D013499:Surface Properties