Effects of chemical gradients on the chemotactic motility of Escherichia coli

Bacterial chemotaxis is a behavior in which motile cells navigate toward food sources or away from toxins, playing a crucial role in their survival. For Escherichia coli and many other species, this movement is typically characterized by undergoing a biased run-and-tumble process along the chemical gradients. In this study, we investigate the chemotactic motility of E. coli under multiple chemical gradients where the cells are subjected to chemoattractant and salt gradients. Using a microfluidic device capable of introducing salt and chemoattractant gradients simultaneously, we observe a drastic change in the swimming behavior, where the cells experience improved motility due to the synergistic effect of chemotaxis and diffusiophoresis. The changes in the swim orientation, run straightness, run speed, and tumble frequency lead to a more robust migration of bacteria toward the chemoattractant. Our findings highlight the potential utility of diffusiophoretic transport in guiding the cells in drug delivery and bioremediation systems.