Run-and-tumble chemotaxis using reinforcement learning

TL;DR

This paper models bacterial run-and-tumble chemotaxis as a reinforcement learning problem, exploring optimal strategies for environmental localization and adaptation in gradient environments.

Contribution

It introduces a novel RL framework for simulating bacterial chemotaxis, analyzing how different strategies perform under various attractant profiles.

Findings

Optimal exploration-exploitation balance improves localization

RL strategies adapt to different attractant gradients

Agent learns environmental distribution effectively

Abstract

Bacterial cells use run-and-tumble motion to climb up attractant concentration gradient in their environment. By extending the uphill runs and shortening the downhill runs the cells migrate towards the higher attractant zones. Motivated by this, we formulate a reinforcement learning (RL) algorithm where an agent moves in one dimension in the presence of an attractant gradient. The agent can perform two actions: either persistent motion in the same direction or reversal of direction. We assign costs for these actions based on the recent history of the agent's trajectory. We ask the question: which RL strategy works best in different types of attractant environment. We quantify efficiency of the RL strategy by the ability of the agent (a) to localize in the favorable zones after large times, and (b) to learn about its complete environment. Depending on the attractant profile and the initial condition, we find an optimum balance is needed between exploration and exploitation to ensure the most efficient performance.