Wall teichoic acids regulate peptidoglycan synthesis by paving cell wall microstructure

The Gram-positive cell wall is a rigid polysaccharide-peptide network that bears the cell’s turgor pressure and confers cell shape. In rod-shaped bacteria, the Rod complex inserts peptidoglycan polymers into the cell wall circumferentially, generating material anisotropy that promotes anisotropic growth. Wall teichoic acids, an abundant, non-load-bearing component of the Gram-positive cell wall, are also essential for rod-shape for unknown reasons. Here, we report a direct role for wall teichoic acids in anisotropic peptidoglycan synthesis. We show that wall teichoic acids provide a cohesive cell wall substrate that is required for Rod complex activity; conversely, removing wall teichoic acids yields a porous cell wall incapable of sustaining Rod complex activity. Consistent with this, cell elongation and Rod complex motion arrest in cells depleted for wall teichoic acids, but resume following hyperosmotic shocks that contract the cell wall. We further show that cells lacking wall teichoic acids rely instead on the bifunctional peptidoglycan synthesis enzyme PBP1, whose isotropic peptidoglycan synthesis is responsible for the subsequent growth and loss of shape. Taken together, these findings reveal that the microstructure of the Gram-positive cell wall is an essential regulatory factor in its own synthesis.