Surfing biological surfaces: exploiting the nucleoid for partition and transport in bacteria

The ParA family of ATPases is responsible for transporting bacterial chromosomes, plasmids and large protein machineries. ParAs pattern the nucleoid in vivo, but how patterning functions or is exploited in transport is of considerable debate. Here we discuss the process of self-organization into patterns on the bacterial nucleoid and explore how it relates to the molecular mechanism of ParA action. We review ParA-mediated DNA partition as a general mechanism of how ATP-driven protein gradients on biological surfaces can result in spatial organization on a mesoscale. We also discuss how the nucleoid acts as a formidable diffusion barrier for large bodies in the cell, and make the case that the ParA family evolved to overcome the barrier by exploiting the nucleoid as a matrix for movement.