FIG 1.

PG synthesis in Gram-negative bacteria. PG synthesis in Gram-negative bacteria is conserved and proceeds in three distinct steps. The process starts with the biosynthesis of monosaccharide-peptide precursors in the cytoplasm followed by the formation of lipid I and lipid II at the cell membrane. Lipid II is then oriented from the cytoplasm to the periplasm, where PG assembly occurs. In rod-shaped bacteria, cytoskeletal proteins guide the location of PG synthesis at different stages of the cell cycle. During cell division, FtsZ organizes the divisome, which synthesizes PG at the division site. For clarity, we include only a subset of cell division proteins in the diagram. During cell elongation, the elongasome is associated with MreB, which directs PG synthesis at the sidewalls. See text for details. GlcNAc, N-acetylglucosamine; MurNAc, N-acetylmuramic acid; Ala, alanine; Glu, glutamic acid; Dap, meso-diaminopimelic acid.