Elasticity of the rod-shaped Gram-negative eubacteria

We report a theoretical calculation of the elasticity of the peptidoglycan network, the only stress-bearing part of rod-shaped Gram-negative eubacteri a. The peptidoglycan network consists of elastic peptides and inextensible glycan strands, and it has been proposed that the latter form zigzag filame nts along the circumference of the cylindrical bacterial shell. The zigzag geometry of the glycan strands gives rise to nonlinear elastic behavior. Th e four elastic moduli of the peptidoglycan network depend on its stressed s tate. For a bacterium under physiological conditions the elasticity is prop ortional to the bacterial turgor pressure. Our results are in good agreemen t with recent measurements.