Regulation of cell size and shape in bacteria

Bacterial cell shape is physically determined by the peptidoglycan cell wall. During growth the cell thus has to cleave existing peptidoglycan and insert new peptidoglycan to increase its cell envelope. The process of cleavage and insertion is thought to be carried out by a complex of hydrolytic and synthetic enzymes that interact with the cytoplasmic cytoskeleton. I will present our observations of the MreB cytoskeleton and of individual proteins that are part of the 'rod complex' relevant for cell elongation, using high-resolution single-molecule microscopy in live cells. I will also discuss various ways to perturb the cell-wall expansion process to reveal the determinants of robust cell-wall architecture and shape.

While the shape of the newly forming cell is governed by the localization of cell-wall modifying enzymes, the rate of cell-volume expansion is governed by enzyme activity and enzyme abundance – through a combination of transcriptional, translational, and post-translational regulation. I will discuss the possible contributions of these different mechanisms to reliable cell-wall expansion and other physiological processes in fluctuating physiological conditions.