When active filaments are subjected to focused light, they tend to gather and form stable shapes along the edges of the illuminated region. Researchers at the Max Planck Institute for Dynamics and Self-Organization (MPI-DS) have created a model to simulate how thread-like living matter naturally organizes itself. This model offers valuable insights for potential technical uses in building structures.
Filamentous cyanobacteria cluster in regions with optimal light conditions, utilizing light energy for photosynthesis. These microorganisms typically form extensive chains made up of numerous cells. However, these thread-like entities can only advance or retreat — when they exit the lit area, they switch direction and consequently stay within the light zone. Scientists at MPI-DS have explored the organizational patterns that emerge from this behavior. They discovered that it is the interplay between multiple filaments that drives the cyanobacteria to align themselves along the inner edge of the illuminated surface, creating stable formations.
To investigate this, the researchers prepared and illuminated various cultures of cyanobacteria in Petri dishes. By using slides to create distinct light patterns, they observed how the bacteria self-organized. When a circular light pattern was used, the bacteria predominantly clustered at the boundary of the illuminated area. Similarly, with triangular, trapezoidal, or other shapes, unique filament patterns were observed near the light’s edges. “It’s fascinating that the bacteria can organize around complex shapes and curves, even though their movement is limited to forward and backward,” explains Stefan Karpitschka, group leader at MPI-DS and professor at the University of Konstanz. “This is a classic example of emergence, where a cohesive structure arises independently from the simple behavior of individual filaments,” he adds.
The findings from these experiments and the resulting model can also apply to other living entities with similar structures. “Our model doesn’t specify the biological details of the bacteria,” notes Leila Abbaspour, who is a co-lead author of the study alongside Maximilian Kurjahn. “This collective behavior can also manifest in analogous systems, allowing active filaments to organize themselves based on environmental sensory cues, despite their linear movement,” Kurjahn explains.
Consequently, the results of this research hold significant promise for the development of ‘smart’ textiles or materials, for instance. These innovative structures and fabrics rely on how individual fibers and active filaments are arranged. Mechanisms of self-assembly like these could pave the way for creating new, innovative materials.
