From the regulation of peptidoglycan synthesis to bacterial growth and morphology

The peptidoglycan sacculus maintains bacterial cell shape and provides mechanical strength to resist osmotic challenge. In this Review, Vollmer and colleagues describe recent insights into the mechanisms of peptidoglycan synthesis in Gram-negative bacteria and how this process is regulated by cytoskeletal and outer-membrane components. How bacteria grow and divide while retaining a defined shape is a fundamental question in microbiology, but technological advances are now driving a new understanding of how the shape-maintaining bacterial peptidoglycan sacculus grows. In this Review, we highlight the relationship between peptidoglycan synthesis complexes and cytoskeletal elements, as well as recent evidence that peptidoglycan growth is regulated from outside the sacculus in Gram-negative bacteria. We also discuss how growth of the sacculus is sensitive to mechanical force and nutritional status, and describe the roles of peptidoglycan hydrolases in generating cell shape and of D-amino acids in sacculus remodelling.