Bacterial chemotaxis promotes spatial interactions and nutrient exchange between motile cells

Microbial symbiosis is important across many ecological systems, including in marine, aquatic and terrestrial environments. Despite its prevalence, understanding the mechanisms by which cell-cell interactions are established and maintained remains limited. Recent work has shown that chemotaxis – the directed motion of cells in response to chemical gradients – enhances metabolic exchanges between motile marine bacteria and non-motile picophytoplankton cells. However, resolving the spatial interactions between comoving chemotactic bacteria, and the implications for their capacity to share nutrients – remains unexplored. Here, we calculate the nutrient concentration profile produced by a motile source, exuding nutrients at a constant rate, and use this to develop an agent-based simulation resolving interactions between individual bacteria. We find that bacteria performing chemotaxis experience on average a 2-fold to 10-fold enhancement in their nutrient exposure when targeting moving sources, relative to non-chemotactic strains. This suggests that chemotaxis may represent an important behavioural strategy for nutrient acquisition in the open ocean.