Biosynthesis of the peptidoglycan of bacterial cell walls. XII. Inhibition of cross-linking by penicillins and cephalosporins: studies in Staphylococcus aureus in vivo.

摘要: Abstract An uncross-linked monomer (nascent peptidoglycan unit) accumulates in cells of Staphylococcus aureus treated with low concentrations penicillin G or ampicillin, methicillin, cephalothin. The has been isolated, and analyses indicate that it represents a prefabricated subunit the wall bearing both d-alanine residues its pentapeptide precursor as well an open pentaglycine chain. Pulse labeling experiments this unit is direct cross-linked cross-linking inhibited by G. At high G, synthesis ceases abruptly no accumulation nascent units observed. These data have obtained support hypothesis penicillins are substrate analogues d-alanyl-d-alanine end they acylate transpeptidase which catalyzes reaction. may also provide explanation paradoxical observation killing rate S. higher at than antibiotic. In presence weakened be formed, thus rendering organisms more susceptible to lysis where ceases.