Teichoic acids as organizing centers for growth and shape in Bacillus subtilis

The Gram-positive cell wall is a rigid, sugar-peptide meshwork that constrains the cell's immense turgor pressure and confers cell shape. Specifically, rod shape is maintained through the circumferential orientation of the cell wall's peptidoglycan backbone by the Rod complex. Wall teichoic acids (WTAs) contribute up to 50% of the Gram-positive cell wall by mass and are known to assist with divalent cation homeostasis. However, a longstanding mystery is why preventing the first dedicated step of wall teichoic acid synthesis causes the complete loss of rod-shape. We used dynamical, quantitative microscopy to demonstrate that inhibiting wall teichoic acid synthesis causes a fundamental re-organization of peptidoglycan synthesis. Inhibiting WTA synthesis prompts a rapid decline in Rod complex activity coincident with a growth rate decrease. We further show that subsequent growth and the loss of rod-shape are then sustained by a separate pathway that inserts peptidoglycan isotropically. We posit that WTAs provide a fulcrum that quantitatively tunes the balance between oriented and isotropic cell wall synthesis, thereby maintaining cell shape and growth rate.