Medical Research Council - London Institute of Medical Sciences

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How mixed populations of bacteria mingle and segregate

16 November 2022

Swarm Regards

Organisms living side by side produce a new form of life – a community. While ecosystems can be miles wide, this tiny swarm of bacteria is just establishing itself on a lab dish. Its two bacterial species, Bacillus subtilis (highlighted in red) and Pseudomonas aeruginosa (green), behave very differently, growing and dividing on different time scales and moving at different speeds. Here researchers watch as they mingle but not completely, keeping themselves to themselves but sometimes cooperating – with B. subtilis seeming to improve how the P. aeruginosa swarms. Bacterial communities, including those that stubbornly colonise surfaces in hospitals, are a natural form of active matter – a complex balance of biological behaviours and physical properties that crop up when 'things' move together. But even considering these factors, the team believe there are hidden subtleties still to discover – including the ways bacteria to recognise their own species when moving through the crowd.

Written by John Ankers

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