Reverse gear after a collision: how bacteria find their way through crowds
EPFL researchers show that the pathogen Pseudomonas aeruginosa senses collisions with its neighbours and reverses within seconds. This keeps the colony mobile and helps it spread.
Photo: Benoit-Joseph Laventie / Wikimedia Commons, CC BY 4.0 (cropped and resized)
Video: YouTube · EPFL · youtube.com
Researchers at EPFL led by Alexandre Persat have found that the bacterium Pseudomonas aeruginosa senses when it bumps into its neighbours and reverses direction within seconds. The study was published on 6 October in the journal Nature Microbiology (DOI 10.1038/s41564-026-02505-1), with contributors from the University of California San Diego.
In crowded spots, the frequent reversals keep the cells disordered and mobile. At the edge of a colony, however, they align and move out into open space together. In a tiny maze, normal bacteria explored 92 percent of the area on average and 20 percent reached the exit. A mutant that always moves forward got stuck in dense clusters – only one percent made it out within four hours.
Order in the bacterial swarm is therefore an actively regulated state rather than just a result of physical forces. According to EPFL, the mechanism may help the pathogen spread through tissue during infections and form biofilms.