PT  - JOURNAL ARTICLE
AU  - Mao, Hanbin
AU  - Cremer, Paul S.
AU  - Manson, Michael D.
TI  - A sensitive, versatile microfluidic assay for bacterial chemotaxis
AID  - 10.1073/pnas.0931258100
DP  - 2003 Apr 29
TA  - Proceedings of the National Academy of Sciences
PG  - 5449--5454
VI  - 100
IP  - 9
4099  - http://www.pnas.org/content/100/9/5449.short
4100  - http://www.pnas.org/content/100/9/5449.full
SO  - Proc Natl Acad Sci USA2003 Apr 29; 100
AB  - We have developed a microfluidic assay for bacterial chemotaxis in which a gradient of chemoeffectors is established inside a microchannel via diffusion between parallel streams of liquid in laminar flow. The random motility and chemotactic responses to l-aspartate, l-serine, l-leucine, and Ni2+ of WT and chemotactic-mutant strains of Escherichia coli were measured. Migration of the cells was quantified by counting the cells accumulating in each of 22 outlet ports. The sensitivity of the assay is attested to by the significant response of WT cells to 3.2 nM l-aspartate, a concentration three orders of magnitude lower than the detection limit in the standard capillary assay. The response to repellents was as robust and easily recorded as the attractant response. A surprising discovery was that l-leucine is sensed by Tar as an attractant at low concentrations and by Tsr as a repellent at higher concentrations. This assay offers superior performance and convenience relative to the existing assays to measure bacterial tactic responses, and it is flexible enough to be used in a wide range of different applications. CPC,chemotaxis partition coefficient;CMC,chemotactic migration coefficient