Rotate into shape: MreB and bacterial morphogenesis

Abstract

EMBO J 30 24, 4931–4941 (2011); published online September 30 2011

MreB, the bacterial actin homologue, plays a vital role in determining cell shape, but the mechanisms by which it actually functions have remained largely mysterious. Recent studies now shed new light on MreB, demonstrating that it associates with many cell-wall synthesis enzymes, including a newly identified family of proteins that mediate teichoic acid synthesis in Gram-positive bacteria. Furthermore, MreB filaments dynamically rotate around the cell circumference in a manner dependent on the cell-wall assembly machinery. Thus, MreB may function to spatially organize the enzymatic activities required for proper bacterial growth (see Figure 1).

Figure 1

Potential functions of the MreB cytoskeleton in regulating cell shape. (A) MreB (dark blue) recruits several classes of enzymes involved in cell-wall synthesis to the sites of peptidoglycan (PG) and wall teichoic acids (WTAs) insertion. In many Gram-negative (left) and Gram-positive (right) bacteria, these enzymes include the PG assembly PBP enzymes (brown), the PG-precursor synthesizing Mur enzymes (purple), MreC (green), and other transmembrane proteins involved in cell elongation such as RodA, RodZ, and MreD (red). The WTA synthesizing LytR–Cps2A–Psr (LCP) enzymes (blue) also associate with MreB in Gram positives. (B) By restricting insertion of new glycan strands (green) and peptide ponds (red) to sites close to MreB filaments (magenta), the cell might robustly maintain rod-like shape during growth.