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7101714 
Journal Article 
Direct Upstream Motility in Escherichia coli 
Kaya, T; Koser, Hur; , 
2012 
Yes 
Biophysical Journal
ISSN: 0006-3495
EISSN: 1542-0086 
CELL PRESS 
CAMBRIDGE 
1514-1523 
22500751 
WOS:000302443100006 
We provide an experimental demonstration of positive rheotaxis (rapid and continuous upstream motility) in wild-type Escherichia colt freely swimming over a surface. This hydrodynamic phenomenon is dominant below a critical shear rate and robust against Brownian motion and cell tumbling. We deduce that individual bacteria entering a flow system can rapidly migrate upstream (>20 mu m/s) much faster than a gradually advancing biofilm. Given a bacterial population with a distribution of sizes and swim speeds, local shear rate near the surface determines the dominant hydrodynamic mode for motility, i.e., circular or random trajectories for low shear rates, positive rheotaxis for moderate flow, and sideways swimming at higher shear rates. Faster swimmers can move upstream more rapidly and at higher shear rates, as expected. Interestingly, we also find on average that both swim speed and upstream motility are independent of cell aspect ratio.