Biophysics: Amin Doostmohammadi publishes in Nature Physics

An international collaboration between Amin Doostmohammadi and researchers at Oxford University and University of Sheffield has revealed that colonies of slow moving bacteria can expand significantly quicker than their fast moving counterparts. The group combined genetics, experiments, custom image analysis algorithms and theoretical physics to investigate the efficiency of the bacterial invasion. It turned out that bacteria move slowly and prudently in order to avoid crashes and jams, making them capable of moving efficiently in dense and massive, multi-million population, crowds. The result may have implications for how we treat infections in a future in which multi-resistent bacteria, immune to antibiotics, pose a threat to human
health. The result of Amin Doostmohammmadi and collaborators has just been published in Nature Physics.

Certain bacteria move around by grabbing the surfaces with tiny 'feet' called pili. The researchers set up an experiment in which they modified the individual bacteria by increasing the number of pili, all other features or properties remaining unchanged. The individual bacteria were now able to move approximately two times faster than before, and the researchers asked the question if this enhancement of the individual’s abilities would also enhance the population’s ability to invade new territories. The group literally made a race between the fast moving and the slow moving colonies. Counter-intuitively, the genetically enhanced fast
population was overtaken by the slower moving wildtype bacteria population. “A mutant with a larger number of pili could move more rapidly than the wildtype on an individual level, but in large groups they tended to crash into one another. These collisions rotate the mutant cells vertically and trap them in place. As a result, the slower moving wildtype cells can move past them and ultimately win the race into new territory”, explains Amin Doostmohammadi. The results could eventually be used to limit spread of unwanted bacteria by tweaking slightly their physical attributes, thus making them move less efficiently.