Living on the edge: transfer and traffic of E. coli in a confined flow.

We quantitatively study the transport of E. coli near the walls of confined microfluidic channels, and in more detail along the edges formed by the interception of two perpendicular walls. Our experiments establish the connection between bacterial motion at the flat surface and at the edges and demonstrate the robustness of the upstream motion at the edges. Upstream migration of E. coli at the edges is possible at much larger flow rates compared to motion at the flat surfaces. Interestingly, the speed of bacteria at the edges mainly results from collisions between bacteria moving along this single line. We show that upstream motion not only takes place at the edge but also in an "edge boundary layer" whose size varies with the applied flow rate. We quantify the bacterial fluxes along the bottom walls and the edges and show that they result from both the transport velocity of bacteria and the decrease of surface concentration with increasing flow rate due to erosion processes. We rationalize our findings as a function of local variations in the shear rate in the rectangular channels and hydrodynamic attractive forces between bacteria and walls.

[1]  L. G. Leal,et al.  Advanced Transport Phenomena: Fluid Mechanics and Convective Transport Processes , 2007 .

[2]  Roman Stocker,et al.  Bacterial rheotaxis , 2012, Proceedings of the National Academy of Sciences.

[3]  K. Jacobs Introduction to Microfluidics. By Patrick Tabeling. , 2006 .

[4]  Roman Stocker,et al.  Bacterial transport suppressed by fluid shear , 2014, Nature Physics.

[5]  David Saintillan,et al.  Transport of a dilute active suspension in pressure-driven channel flow , 2015, Journal of Fluid Mechanics.

[6]  R. Di Leonardo,et al.  Swimming with an image. , 2011, Physical review letters.

[7]  Jörn Dunkel,et al.  Rheotaxis facilitates upstream navigation of mammalian sperm cells , 2014, eLife.

[8]  Roman Stocker,et al.  Failed escape: solid surfaces prevent tumbling of Escherichia coli. , 2014, Physical review letters.

[9]  Patrick T. Underhill,et al.  Impact of external flow on the dynamics of swimming microorganisms near surfaces , 2014, Journal of physics. Condensed matter : an Institute of Physics journal.

[10]  D. Clapham,et al.  Rheotaxis Guides Mammalian Sperm , 2013, Current Biology.

[11]  Flow-controlled densification and anomalous dispersion of E. coli through a constriction , 2013 .

[12]  F. Oosawa,et al.  Effect of Intracellular pH on Rotational Speed of Bacterial Flagellar Motors , 2003, Journal of bacteriology.

[13]  Jay X. Tang,et al.  Accumulation of microswimmers near a surface mediated by collision and rotational Brownian motion. , 2009, Physical review letters.

[14]  George M Whitesides,et al.  Swimming in circles: motion of bacteria near solid boundaries. , 2005, Biophysical journal.

[15]  J. Dunkel,et al.  Fluid dynamics and noise in bacterial cell–cell and cell–surface scattering , 2011, Proceedings of the National Academy of Sciences.

[16]  Eric Lauga,et al.  Hydrodynamic attraction of swimming microorganisms by surfaces. , 2008, Physical review letters.

[17]  Roman Stocker,et al.  Separation of microscale chiral objects by shear flow. , 2009, Physical review letters.

[18]  Howard C. Berg,et al.  On Torque and Tumbling in Swimming Escherichia coli , 2006, Journal of bacteriology.

[19]  D. Koch,et al.  Emergence of upstream swimming via a hydrodynamic transition. , 2015, Physical review letters.

[20]  Harold Auradou,et al.  Turning Bacteria Suspensions into Superfluids. , 2015, Physical review letters.

[21]  Howard C. Berg,et al.  E. coli in Motion , 2003 .

[22]  L. Fu,et al.  Probing neutral Majorana fermion edge modes with charge transport. , 2009, Physical review letters.

[23]  H. Koser,et al.  Direct upstream motility in Escherichia coli. , 2012, Biophysical journal.

[24]  Jérémie Gachelin Rhéologie et comportement de suspensions de Escherichia Coli en milieux confinés , 2014 .

[25]  H. Berg,et al.  Three-dimensional tracking of motile bacteria near a solid planar surface. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[26]  W. Tian,et al.  Introduction to Microfluidics , 2008 .

[27]  H. Stark,et al.  Detention Times of Microswimmers Close to Surfaces: Influence of Hydrodynamic Interactions and Noise. , 2014, Physical review letters.

[28]  H. Koser,et al.  Hydrodynamic surface interactions enable Escherichia coli to seek efficient routes to swim upstream. , 2007, Physical review letters.