"Figure 2.7: Peptidoglycan is composed of polymers of alternating NAM and NAG subunits, which are cross-linked by peptide bridges linking NAM subunits from various glycan chains. (c) Rice University. OpenStax Microbiology. CC BY 4.0. https://openstax.org/details/books/microbiology . Figure 2.8: Bacteria contain two common cell wall structural types. (c) Rice University. OpenStax Microbiology. CC BY 4.0. Modification of work (c) Franciscosp2 “Bacteria cell wall2”. CC BY 3.0 Unported. https://commons.wikimedia.org/wiki/File:Bacteria_cell_wall2.svg"