Turnover of the Cell Wall Peptidoglycan during Growth of Neisseria gonorrhoeae and Escherichia coli. Relative Stability of Newly Synthesized Material

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Abstract
The peptidoglycan of several strains of N. gonorrhoeae and E. coli turned over during exponential growth as monitored by the loss of radioactivity (supplied as [14C]glucosamine) from sodium dodecyl sulfate insoluble material. No turnover of the peptide side chains of E. coli peptidoglycan was observed (monitored by diamino[3H]pimelic acid) even though turnover of glycan material was occurring. Turnover rates of 9-15% per generation were recoreded for all of the N. gonorrhoeae strains studied except for the autolytic variant RD5, which showed a higher rate of turnover (20-26% per generation). In contrast to previous interpretations, these rates of turnover were not affected by benzylpenicillin, unless sufficient antibiotic was present to affect culture turbidity, when lysis occurred. Examination of the fragments (monomer, dimer and their O-acetylated counterparts, and oligomers) produced by Chalaropsis B muramidase treatment of prelabeled peptidoglycan revealed that no fraction of the peptidoglycan was immune from turnover. However, peptidoglycan pulse-labeled for only 10 min did not show immediate turnover. The lapse of time before turnover commenced was strain dependent, with a maximum value of 1.5 generations. This work confirms that the peptidoglycan of N. gonorrhoeae undergoes a period of maturation and suggests that only mature peptidoglycan turns over.

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