Abstract
A mutant of E. coli was constructed with deletions of the genes encoding pencillin-binding protein 5 (dacA) and penicillin-binding protein 6 (dacC). The construction of this mutant establishes that the complete loss of the 2 most of abundant species of penicillin-binding proteins can be tolerated by E. coli. The double deletion mutant had the same growth rate and morphology as an isogenic dacA+ dacC+ strain.