ZERO ORDER KINETICS OF CELL-WALL TURNOVER IN STAPHYLOCOCCUS-AUREUS

Cells exponentially grown from four strains of S. aureus (SG 511, H, 52A5G, and 248 PN-1) and uniformly labeled in their walls with3H-N-acetylglucosamine, were found to turn over their old walls at constant rates of up to 25% per generation. Wall turnover was not observed to follow first order kinetics, thus ruling out the implication that maintenance of normal wall thickness was achieved by a random distribution of new wall components in the old wall. Instead, wall turnover in all cases strictly followed zero order kinetics, indicating that newly synthesized wall material was placed layer by layer beneath the inner surface of the old cell wall. This finding correlates with evidence obtained from earlier electron microscopic investigations into the regeneration of the staphylococcal cell wall after chloramphenicol treatment. Based on the experimental data presented, a simplified model for wall turnover of the growing staphylococcal cell was proposed. The model also takes into account the finding, derived from additional experiments with strain SG 511, that the total cell wall turned over at a somewhat higher rate than the old portions of the wall. The rates of cell wall turnover found in S. aureus SG 511 are the highest reported to date for pathogenic bacteria. The medical implications of this finding were discussed. © 1979 Springer-Verlag.