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Applied and Environmental Microbiology, July 2009, p. 4557-4564, Vol. 75, No. 13
0099-2240/09/$08.00+0     doi:10.1128/AEM.02952-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Flow-Based Microfluidic Device for Quantifying Bacterial Chemotaxis in Stable, Competing Gradients{triangledown}

Derek L. Englert,1 Michael D. Manson,2 and Arul Jayaraman1,3*

Artie McFerrin Department of Chemical Engineering,1 Department of Biology,2 Department of Biomedical Engineering, Texas A&M University, College Station, Texas 778433

Received 28 December 2008/ Accepted 27 April 2009

Chemotaxis is the migration of cells in gradients of chemoeffector molecules. Although multiple, competing gradients must often coexist in nature, conventional approaches for investigating bacterial chemotaxis are suboptimal for quantifying migration in response to gradients of multiple signals. In this work, we developed a microfluidic device for generating precise and stable gradients of signaling molecules. We used the device to investigate the effects of individual and combined chemoeffector gradients on Escherichia coli chemotaxis. Laminar flow-based diffusive mixing was used to generate gradients, and the chemotactic responses of cells expressing green fluorescent protein were determined using fluorescence microscopy. Quantification of the migration profiles indicated that E. coli was attracted to the quorum-sensing molecule autoinducer-2 (AI-2) but was repelled from the stationary-phase signal indole. Cells also migrated toward higher concentrations of isatin (indole-2,3-dione), an oxidized derivative of indole. Attraction to AI-2 overcame repulsion by indole in equal, competing gradients. Our data suggest that concentration-dependent interactions between attractant and repellent signals may be important determinants of bacterial colonization of the gut.

* Corresponding author. Mailing address: Artie McFerrin Department of Chemical Engineering, Texas A&M University, 222 Jack E. Brown Engineering Building, 3122 TAMU, College Station, TX 77843-3122. Phone: (979) 845-3306. Fax: (979) 845-6446. E-mail: arulj{at}tamu.edu

{triangledown} Published ahead of print on 1 May 2009.

Applied and Environmental Microbiology, July 2009, p. 4557-4564, Vol. 75, No. 13
0099-2240/09/$08.00+0     doi:10.1128/AEM.02952-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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