A vital spark, or something more mundane?

Self-organising microtubules

Self-organisation is a subject that has scientists dribbling with excitement, but not in the same way that believers in the supernatural read intelligent design and other magic into natural behaviour such as the collective motion of flocks of birds and fish, or nanoparticles suspended in test tube solutions.

Modelled as an emergent property of complex systems, self-organisation is a naturalistic phenomenon, with no need for any élan vital. Spontaneous collective motion may be complex or chaotic, but still it is deterministic.

Examples of self-organisation abound in nature, but a detailed understanding of the underlying mechanisms is made difficult owing to a relative lack of quantitative data. Dynamical modelling of murmurating starlings and the like has shed some light on the interaction between individual elements of self-organising collectives, but controlled experiments are needed in order to pin down the physics involved.

Step forward biologist Kazuhiro Oiwa and colleagues, whose in vitro experiment with sub-cellular protein filaments known as microtubules driven by molecular motors shows them organising themselves into large-scale vortices. The researchers say that the behaviour can be explained simply in terms of local interactions in which the microtubules have a tendency to become aligned on collision, with the on average 15 micron microtubules self-organising at high densities into vortices with diameters approaching half a millimetre.

The key is local interactions between individual elements of a large-scale, self-organising collective, and the researchers suggest that their findings may represent a novel mechanism for pattern formation in active systems generally.

Further reading

Sumino et al., “Large-scale vortex lattice emerging from collectively moving microtubules”, Nature 483, 448 (2012)