Bacterial chemotaxis capillary assays

Bainer, R, Park, H., and Cluzel, P. (2003) A high-throughput capillary assay for bacterial chemotaxis. /. Microbiol. Methods 55, 315-319. 

Rgure 10. Capillary assay for positive chemotaxis. (a) A capillary containing a chemoattractant [reddish color) is placed within a bacterial suspension (the bacteria are represented by short lines). Initially the bacteria are randomly distributed In the suspension and their density is equal throughout. With time the cells concentrate near the capillary opening and then (usually after 30-60 min from the initiation of the assay in the case of E. coli and similar bacteria) they accumulate within the capillary, (b) Number of bacteria in the capillary as a function of the concentrations of a chemoattractant and of an inert chemical. 

Most studies of bacterial chemotaxis have used some form of the capillary tube assay originally described by Pfeffer (1884) and later modified by Adler (1973). This method, often referred to as the Adler method, measures the movement of bacteria into a capillary that has been filled with a test chemical. While the original method examined chemotaxis in Escherichia coli, this method, with minor modifications, has proven effective for measuring chemotaxis in marine microorganisms. 

Figure 1.2. Diagram of a typical apparatus used in bacterial chemotaxis assays. The U-tube and cover glass form a chamber into which a bacterial suspension is added. Capillaries containing potential chemoattractants are then immersed into the chamber and the number of bacteria that move into the capillary are counted relative to a control. Modified from Adler (1973).

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