Spatiotemporal organization of microbial cells by protein concentration gradients

The formation of protein concentration gradients is an effective means to restrict the activity of regulatory factors in space, thereby critically contributing to the spatiotemporal organization of biological systems. Although widely observed for extracellular proteins involved in tissue patterning, the implementation of this regulatory strategy was thought to be impossible in single, micron-sized cells. Recently, however, several intracellular proteins were shown to establish gradient-like distribution patterns, thereby relaying positional information to their downstream targets. In this review, we discuss gradient-forming systems from different microbial species, with an emphasis on their mode of action and the common principles that underlie their function.