Segregation of lipids to cellular poles

Abstract

A simple mechanism is suggested for the segregation of lipid domains to the poles of bacterial cells. The cell is modeled as a capsule (or spherocylinder), and the lipids are particles that are confined to the surface of the capsule. The lipid particles interact via a short-ranged Lennard-Jones interaction, and single particles are not curvature sensing in any way. When the temperature is decreased, liquid clusters nucleate on the surface. These domains then segregate to the spherical caps of the capsule. The segregation is scale invariant, i.e., it happens whether the capsule is large, of the order or micrometers, or of the order of tens of nanometers, for particles of size ∼1 nm. We propose that the slight energetic preference for the curved regions between next nearest neighbors is sufficient to promote a large scale segregation. The phenomenon is general, i.e., as long as lipids make domains, e.g., rafts, they are predicted to be preferentially found at the poles.