Official web site of Takeuchi Lab, Univ. Tokyo

Searching for universal laws behind the beauty of collective behavior

What is active matter physics? A flock of starlings circling the dusk sky like a gigantic black ghost. Or a school of sardines creating massive whirlpools in the sea to fool their enemies. Or, on land rather than at sea, a colony of army ants marching in circles to form a hill-like structure. All of these examples display magnificent collective behavior as if there was a leader somewhere in control. However, there is no leader, no choreographer. How is such neatly ordered collective behavior possible? That is the mystery that Daiki Nishiguchi is tackling. One could be forgiven for thinking that his research pertains to biology and has nothing to do with physics. Yet, “This is active matter physics, a field within non-equilibrium statistical physics,” he clarifies.

Microbial 'Jenga' : how bacteria stack

Colonies of rod-shaped bacteria such as Escherichia coli often form dense aggregates called biofilm. Think dental plaques and slimy films on your kitchen sink. Biofilms can cause various problems in medicine (e.g., bacterial infection) and industries (e.g., corrosion). Under a powerful microscope, the bacteria look like strokes in van Gogh's paintings. When their population density is high, they form three-dimensional structures. Takuro Shimaya and Kazumasa Takeuchi from the University of Tokyo show that the way the growing but immotile bacterial cells align with each other helps form three-dimensional structures. The findings offer insights into the physics of their dynamics.