Chemotactic Sensitivity of Escherichia coli to Diffusion Perturbations in Narrow Tubes

Diffusion resistance hinders the free chemotactic motility of bacteria through narrow tubes and capillaries. In many such situations, diffusion is significant and often subject to environmental perturbations. This problem has been analyzed through the sensitivities of Escherichia coli cells, a secreted chemoattractant (aspartase) and a nutrient. Differences and similarities among the sensitivity profiles with respect to the three diffusion coefficients reveal useful information about interactions between diffusion and chemotaxis. The results are consistent with the concept of stabilization created by negative feedback, either within the chemosensory network or from outside. Their implications for some real systems are discussed.