- Volume 131, Issue 2, 1985

The peptidoglycan of a number of strains of Neisseria gonorrhoeae and Escherichia coli turned over during exponential growth as monitored by the loss of radioactivity (supplied as [14C]glucosamine) from SDS-insoluble material. However, 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 to 15% per generation were recorded for all of the N. gonorrhoeae strains studied except for the autolytic variant RD5 which showed a higher rate of turnover (20 to 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 prelabelled peptidoglycan revealed that no fraction of the peptidoglycan was immune from turnover. However, peptidoglycan pulse-labelled 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.

Staphylococcus aureus (Wood 46) was grown aerobically and anaerobically in supplemented 3% (w/v) Tryptone Soya Broth medium for 24 h at 37°C. Although the bacterial density achieved was 9 times higher in the aerobic culture, the exoprotein produced per unit of bacterial dry weight was only 1·4 times higher than in the anaerobic culture. However, the SDS-PAGE patterns of extracellular proteins were quite different : the aerobic products occurred almost exclusively in the mol. wt range 15–30000 compared with 30–60000 for those produced anaerobically. The only major component common to both preparations was α-toxin which accounted for 2·4 times more of the total exoprotein under aerobic than under anaerobic conditions.