  Bacteria can chemotactically migrate up attractant gradients by controlling
run-and-tumble motility patterns. In addition to this well-known chemotactic
behaviour, several soil and marine bacterial species perform chemokinesis: they
adjust their swimming speed according to the local concentration of
chemoeffector, with higher speed at higher concentration. A field of attractant
then induces a spatially varying swimming speed, which results in a drift
towards lower attractant concentrations -- contrary to the drift created by
chemotaxis. Here, to explore the biological benefits of chemokinesis and
investigate its impact on the chemotactic response, we extend a
Keller-Segel-type model to include chemokinesis. We apply the model to predict
the dynamics of bacterial populations capable of chemokinesis and chemotaxis in
chemoeffector fields inspired by microfluidic and agar plate migration assays.
We find that chemokinesis combined with chemotaxis not only may enhance the
population response with respect to pure chemotaxis, but also modifies it
qualitatively. We conclude presenting predictions for bacteria around dynamic
finite-size nutrient sources, simulating, e.g., a marine particle or a root. We
show that chemokinesis can reduce the measuring bias that is created by a
decaying attractant gradient.
