Chemotaxis Adler method

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. 

In a generalized Adler method, one end of a capillary tube (1 Xl disposable micropipette, 3 cm long with an internal diameter of 0.2 mm) is flame sealed. The entire capillary tube is then quickly passed through a flame, and while warm, the open end is plunged into a reservoir containing the test chemical dissolved in chemotaxis medium. The liquid is drawn up into the capillary as it cools and the filled capillary is then withdrawn from the reservoir and inserted into a chemotaxis chamber, which is constructed by placing a U-shaped melting point capillary tube between a microscope slide and a coverslip (Fig. 1.2). The chamber is filled with an appropriate chemotaxis medium and inoculated with bacteria so that the final concentration is approximately 6 x 10 cells/ml. After a 1-h incubation, the capillary is removed from the chamber and the exterior rinsed with sterile water. The sealed end of the capillary is then broken and the contents are... 

Adler, J. (1973) A method for measuring chemotaxis and use of the method to determine optimum conditions for chemotaxis by Escherichia coli. J. Gen. Microbiol. 74, 77-91. 

The advantages of the capillary assay are its simplicity, quantitative nature, and high sensitivity. Alternative methods for studying chemotaxis such as the swarm plate method of Adler (1966) require that the chemoattractant be metabolized. This is not necessary in the standard capillary assay. In addition, due to the small size of the chemotaxis chamber, only small amounts of compound are required to perform the experiments. The main disadvantage of this method is that the compound tested must be soluble in the chemotaxis medium. 

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