False positive responses of Campylobacter jejuni when using the chemical-in-plug chemotaxis assay.

Campylobacter jejuni reportedly exhibits chemotactic behavior towards fucose, several amino acids and organic acids, mucin and bile. The chemotaxis of C. jejuni has mainly been studied using the chemical-in-plug chemotaxis assay. In this study, a nonchemotactic mutant (cheY mutant) and nonmotile mutant (flhA mutant) were constructed and used as negative controls in an assay. Apparent zones of accumulation around test plugs containing several amino acids and organic acids were observed with both of the mutants. Our results suggest that positive responses of C. jejuni in the chemical-in-plug assay are not always indicative of chemotaxis.