EVIDENCE FOR N-]O ACETYL MIGRATION AS THE MECHANISM FOR O ACETYLATION OF PEPTIDOGLYCAN IN PROTEUS-MIRABILIS

O-acetylated peptidoglycan was purified from Proteus mirabilis grown in the presence of specifically radiolabelled glucosamine derivatives, and the migration of the radiolabel was monitored. Mild-base hydrolysis of the isolated peptidoglycan (to release ester-linked acetate) from cells grown in the presence of 40-mu-M [acetyl-H-3]N-acetyl-D-glucosamine resulted in the release of [H-3]acetate, as detected by high-pressure liquid chromatography. The inclusion of either acetate, pyruvate, or acetyl phosphate, each at 1 mM final concentration, did not result in a diminution of mild-base-released [H-3]acetate levels. No such release of [H-3] acetate was observed with peptidoglycan isolated from either Escherichia coli incubated with the same radio-label or P. mirabilis grown with [1,6-H-3]N-acetyl-D-glucosamine or D-[1-C-14]glucosamine. These observations support a hypothesis that O acetylation occurs by N --> O acetyl transfer within the sacculus. A decrease in [H-3]acetate release by mild-base hydrolysis was observed with the peptidoglycan of P. mirabilis cultures incubated in the presence of antagonists of peptidoglycan biosynthesis, penicillin G and D-cycloserine. The absence of free-amino sugars in the peptidoglycan of P. mirabilis but the detection of glucosamine in spent culture broths implies that N --> O transacetylation is intimately associated with peptidoglycan turnover.