Effect of D-amino acids on Escherichia coli strains with impaired penicillin-binding proteins.

Escherichia coli cells growing in the presence of some D-amino acids incorporate D-amino acid into the peptidoglycan layer of the cell wall by a mechanism most likely independent of the normal biosynthetic pathway. Analysis of the sensitivity of mutant strains with impaired penicillin-binding proteins (PBP) to D-amino acids indicated that ponB and DD-endopeptidase/DD-carboxypeptidase-I-defective strains are hypersensitive to D-amino acids. D-tryptophan containing peptidoglycan was found to be more susceptible to the action of lytic transglycosilases than native material, which could explain in part the harmful effects of D-amino acids. ponB strains carrying additional mutations suppressing hypersensitivity to D-amino acids have been obtained and the results of their initial characterization are reported.