Abstract

We study the how cells grow and divide in defined shapes by watching the in vivo motions of the enzymes that build the cell wall and the polymers that regulate them. The two primary polymers that define the location and activity of cell wall synthesis enzymes cell shape are homologs of actins and tubulins.  By studying the in vivo motions of these polymers we learn both how their superstructure and dynamics affects their cellular function. We see that both systems use short, curved filaments as orienting rudders, pointing the filaments around the short axis of the cell. We will show how this property functions to create rod-shaped cells through a feedback loop. By studying the dynamics of these polymers in respect to the enzymes we also learn how these polymers and enzymes work together to build the cell wall. Our work shows that the actins involved in cell elongation are stable, functioning solely as rudders that are pulled by the enzyme as cargo. In contrast, the polymers and enzymes of division are functionally flipped: The filaments treadmill, and the treadmilling of the filaments controls the activity of the enzymes.