(A) rpHPLC profile of disaccharide-peptides. Absorbance was recorded at 210 nm (mAU, absorbance units x 103). (B) Identification of disaccharide-peptides by mass spectrometry. The relative abundance of peptidoglycan fragments was estimated as the percentage of the total integrated area. The observed and calculated monoisotopic mass of muropeptides is indicated in Da. GM, GlcNAc-MurNAc; anh, anhydro; R, reduced; Tri, tripeptide L-Ala-γ-D-Glu-DAP (DAP, diaminopimelic acid); Tetra, tetrapeptide L-Ala-γ-D-Glu-DAP-D-Ala; Tri-Gly, tetrapeptide L-Ala-γ-D-Glu-DAP-Gly; Penta, pentapeptide L-Ala-γ-D-Glu-DAP-D-Ala-D-Ala; 3→3, cross-link generated by L,D-transpeptidation.