Cell Wall Peptidoglycan Mutants of Escherichia coli K-12: Existence of Two Clusters of Genes, mra and mrb , for Cell Wall Peptidoglycan Biosynthesis

Temperature-sensitive mutants ofEscherichia coli K-12 which cannot form cell wall peptidoglycan at 42 C were isolated. The thermosensitive steps were characterized biochemically, and the genes coding the enzymes of peptidoglycan synthesis were mapped. These genes were in two clusters: one group, located at about 1.5 min betweenleu andazi , was designated asmra (murein a); the second group, located at about 77.5 min close toargH andmetB , was designated asmrb (murein b, with the ordermetB-argH-mrb ). No simple relations were found between the gene location and the order or localization of enzymes involved in the sequence of reactions of cell wall peptidoglycan biosynthesis.