eLife http://doi.org/bvpz (2016)

Ever wondered how to find your centre? Bacteria do it by exploiting the dynamics of Min proteins, which oscillate from pole to pole until the midplane of the cells' cylindrical geometry becomes clear. For E. coli and many other single-celled organisms, it's a question of utmost importance: they can't divide symmetrically unless they find their centre. And now, Yaron Caspi and Cees Dekker have undertaken the first in vitro study to fully confine the bacterial Min protein system in three-dimensional microfluidic chambers, revealing a rich dynamics that is sensitively dependent on confinement.

Previous studies showed that Min proteins can form rotating spirals and travelling waves instead of the characteristic oscillations when studied in vitro. But theoretical models have had a hard time capturing in vitro and in vivo results simultaneously. Caspi and Dekker's experiments enabled them to construct a phase diagram indicating that spirals give way to pole-to-pole oscillations when confinement is tightened — and to travelling waves when it's relaxed. The study raises the possibility that in vitro and in vivo dynamics arise from fundamentally different symmetry-breaking mechanisms, rather than simply different geometries.