Agenda

Rotate into shape, but how? Actin-like MreB dynamics and morphogenetic function in bacteria.

 RutCarballido-López

INRA, UMR1319 Micalis, F-78352 Jouy-en-Josas, France.

How cells control their shape and size is a long-standing question in cell biology. The peptidoglycan cell wall and the actin-like MreB cytoskeleton are major determinants of cell shape in rod-shaped bacteria. We previously showed that in growing cells MreB proteins, together with other morphogenetic factors, assemble into discrete patches that move processively along peripheral tracks perpendicular to the cell axis. Patch motility is largely powered by cell wall synthesis, and MreB polymers restrict diffusion and orient the motion of patch components in the membrane, thereby orchestrating controlled sidewall elongation. However, little is known about how MreB-associated cell wall biosynthetic complexes are regulated to enable varied grow rates and cell sizes. We have used total internal reflection fluorescence (TIRF) microscopy combined with automated single particle tracking (SPT) analysis to visualize the dynamics and properties of MreB isoformsin Bacillus subtilis and Escherichia colicells growing under different nutrient conditions and upon nutrient shift. We show that although both organisms present a similar mechanism of cell elongation they present distinct strategies to adapt to variation of their growth regime.