Qualitative and quantitative assays for flagellum-mediated chemotaxis

A primary driving force during bacterial evolution was the capacity to access compounds necessary for growth and survival. Since the species of the genus Pseudomonas are characterized by metabolic versatility, these bacteria have developed chemotactic behaviors towards a wide range of different compounds. The specificity of a chemotactic response is determined by the chemoreceptor, which is at the beginning of the signaling cascade and to which chemoattractants and chemorepellents bind. The number of chemoreceptor genes of Pseudomonas species is significantly higher than the average number in motile bacteria. Although some of the receptors have been annotated with a function, the cognate signal molecules for the majority of them still need to be identified. Different qualitative and quantitative methods are presented that can be used to study flagellum-mediated taxis.