Chemotactic response of bacteria to nutrient plumes in heterogenous flow fields

Chemotaxis is the ability of bacteria to sense and react to different chemicals present in their environment. This enhances their ability to bias their motility towards favorable environments and colonize new regions or move away from toxic environments. Here, using microfluidic experiments, we study the chemotactic response of Escherichia coli to ephemeral nutrient plumes emerging from hydrogel arrays in the presence of a heterogeneous flow field. We demonstrate how the interplay between flow and chemotaxis leads to the preferential accumulation of bacteria around the hydrogel obstacles. We discuss the implications of our observations in the context of bacterial chemotaxis and colonization of dissolving organic matter in the oceans and soil.