As the saying goes, slow and steady wins the race! This well-known proverb also applies to bacterial communities when moving to colonize new territories. This is the result of the studies conducted by a team of researchers from the University of Sheffield and the University of Oxford and published in the journal Nature Physics: bacterial groups spread more rapidly over new territory when the individuals inside them move more slowly. The findings may provide new insight into how bacteria move within our body during infections and how to prevent their spreading.

How did researchers get this result? Scientists genetically modified the pathogen Pseudomonas aeruginosa, by engineering fast-moving and slow-moving bacteria to have them compete in a real speed race. By using a combination of molecular genetics, algorithms and mathematics, scientists tracked the movement of hundreds of thousands of bacterial cells simultaneously and measured their motility. Scientists found out that bacteria engineered to individually move faster were actually slower in colonizing new territories than bacteria modified to move slower. When moving in densely packed groups, the faster bacteria tend to crash into one other and rotate vertically, getting stuck. In contrast, slower-moving bacteria avoid this trapping mechanism and generate a more effective collective movement.

To understand these phenomena and describe them physically, scientists used a theory that was originally developed to study materials known as liquid crystals. This research sheds light on the migration of bacteria as they colonize new territories, but it also shows that collective movements such as those relating to flocks of birds or schools of fish also occur in the microscopic world.