# Migration and accumulation of bacteria with chemotaxis and chemokinesis

## TL;DR

This paper extends a mathematical model to include bacterial chemokinesis alongside chemotaxis, revealing how combined behaviors influence bacterial migration and improve responses to nutrient sources in complex environments.

## Contribution

It introduces a Keller-Segel-type model incorporating chemokinesis and analyzes its effects on bacterial migration dynamics and response to chemoeffector fields.

## Key findings

- Chemokinesis enhances bacterial population response when combined with chemotaxis.
- Chemokinesis modifies the migration pattern, potentially reducing bias in nutrient gradient measurements.
- The model predicts bacterial behavior around dynamic nutrient sources like marine particles or roots.

## Abstract

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.