Fig. 4.

Computational simulations suggest that MreB rotation improves rod-like cell shape maintenance. (A) Schematic of cell-wall growth simulations in which the synthesis of new glycan strands (blue) initiates from a single continuous (Upper) or a fragmented (Lower) helical MreB structure (yellow). The glycan strands and peptides are shown in green and red, respectively. The helix angle in A and B is 60°. (B) Threefold elongation of the cell wall on the left by inserting strands from a nonrotating (Upper) or rotating (Lower) single MreB helix. (C) Cell width variability as a function of decreasing MreB helix angle, with (magenta) and without (cyan) MreB rotation. The circles correspond to the examples illustrated in B. (D) Cell diameter variability as a function of an increasing number of MreB fragments for a fixed helix angle of 60° (the helical angle of each fragment). (E) Cell walls were grown from a single nonrotating (Upper) and rotating (Lower) MreB helix with a helix angle of 72° until length doubled, and then were osmotically shocked from 1 atm (Left) to 2 atm (Right). (F) Cell diameter variability as a function of osmotic shock (1 atm corresponds to no osmotic shock).