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  • Open Access

Density-controlled reversal of collective migration in bacterial aerotaxis

Dipanjan Ghosh1,*,†, Brato Chakrabarti2,‡, and Xiang Cheng1,3,§

  • *Contact author: dipanjan.ghosh@ist.ac.at
  • †Present address: Institute of Science and Technology Austria, Klosterneuburg, Austria.
  • ‡Contact author: brato.chakrabarti@icts.res.in
  • §Contact author: xcheng@umn.edu
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Phys. Rev. Research 8, 033059 – Published 14 July, 2026

DOI: https://doi.org/10.1103/y7l1-288v

Abstract

In living matter, chemical gradients that populations generate and reshape often guide collective migration. Bacterial aerotaxis exemplifies this feedback between metabolism and movement, giving rise to unexpected collective behaviors. Here, we combine quantitative experiments, theoretical modeling, and numerical simulations to reveal a striking, density-dependent reversal in the migration of Escherichia coli within self-generated oxygen gradients. At low cell densities, populations retreat from the oxygen-rich interface; at high densities, they move toward it. A biophysical model in which bacteria bias their motion toward an intermediate, metabolically optimal oxygen concentration quantitatively captures this reversal and predicts a critical density at which collective migration ceases, even in the presence of sustained oxygen gradients. These findings reconcile long-standing discrepancies in observations of bacterial aerotaxis and highlight how feedback between metabolism, movement, and environmental shaping governs emergent behaviors in active matter, with potential implications for microbiome ecology.

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Phys. Rev. Research 8, 033059– Published 14 July, 2026
  • Received 13 November 2025
  • Accepted 29 April 2026
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