Most bacteria surround their cytoplasmic membrane with a net-like, elastic heteropolymer, the peptidoglycan sacculus, to protect themselves from bursting due to the turgor and to maintain cell shape. It has been assumed that growing bacteria require peptidoglycan hydrolases to open meshes in the peptidoglycan net allowing the insertion of the newly synthesized material for surface expansion. However, peptidoglycan hydrolases essential for bacterial growth have long remained elusive. In this issue of Molecular Microbiology Singh et al. (2012) report the identification in Escherichia coli of three new DD-endopeptidases (Spr, YdhO and YebA) which are collectively required for peptidoglycan growth. Cells depleted of the three enzymes fail to incorporate new peptidoglycan, indicating that the cleavage of cross-links by the new endopeptidases is needed for surface growth of the sacculus. These results are corroborated by recent data showing that Bacillus subtilis cells require the DL-endopeptidase activity of CwlO or LytE for growth.
© 2012 Blackwell Publishing Ltd.