Biosynthesis of Peptidoglycan in Pseudomonas aeruginosa

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Abstract
Ether‐treated cells of pseudomonas aeruginosa catalyze the formation of crosslinked peptidoglycan from the two nucleotide precursors uridinediphospho‐N‐acetylglucosamine and uridine‐diphospho‐N‐acetylmuramyl‐l‐alanyl‐d‐γ‐glutamyl‐meso‐ diaminopimelyl‐d‐alanyl‐d‐alanine. The main enzymatic reactions of biosynthesis were similar to those found in Escherichia coli. Part of the reaction products were soluble in 4% sodium dodecylsulfate whereas the other part was covalently bound to the preexisting cell wall peptidoglycan sacculus. The incorporation into cell wall is carried out by a transpeptidation reaction in which the nascent peptidoglycan functions mainly as the donor and the preexisting one as acceptor. The detergent‐soluble peptidoglycan is composed of partially crosslinked peptidoglycan strands as well as low‐molecular‐weight peptidoglycan fragments. Pulse‐chase biosynthesis experiments show that the detergent‐soluble peptidoglycan is an intermediate that eventually becomes covalently bound to the wall. The dd‐carboxypeptidase activity of P. aeruginosa is membrane‐bound and does not hydrolyse C‐terminal d‐alanine residues from the l‐lysine‐containing nucleotide‐precursor analogue. An ld‐carboxypeptidase was also detected in P. aeruginosa.