Murein and lipopolysaccharide biosynthesis in synchronized cells of Escherichia coli K 12 and the effect of penicillin G, mecillinam and nalidixic acid

Abstract

The incorporation of radioactive N-acetyl-glucosamine into murein and lipopolysaccharide of synchronized cells of Escherichia coli K 12 was followed over 100 min in the presence of antibiotics. At 20 min intervals cell walls were prepared. Lipopolysaccharide and murein sacculi were isolated and the radioactivity was quantified in both polymers. Labelled, newly synthesized murein was characterized according to murein subunits linked to lipoprotein, and the degree of crosslinkage. Furthermore, murein subunits containing anhydromuramic acid were determined, permitting the calculation of the average glycan chain length. The results indicated that penicillin G at 30 micrograms/ml stimulated the incorporation of new murein subunits into sacculi followed by a sudden increase in lipopolysaccharide incorporation into the outer membrane. The degree of crosslinkage in murein synthesized in the presence of 30 micrograms/ml penicillin G was higher than in the control, and almost twice as high as in murein synthesized in the presence of 20 micrograms/ml nalidixic acid. Both antibiotics inhibited cell division at the concentrations indicated. Murein synthesized in the presence of 2 micrograms/ml mecillinam also showed higher crosslinkage. However, about twice as much anhydromuramic acid-containing subunits were observed as in the control. At the same time lipopolysaccharide incorporation into the outer membrane was stimulated two- to three-fold.

Function of penicillin-binding protein 2 in viability and morphology of Pseudomonas aeruginosa

“…Muropeptide maps generated by analytical HPLC indicated that the overall distribution of the mutanolysin-derived oligomuropeptides was very similar for the three preparations (data not shown). Total cross-linking was determined based on these analyses and, unlike the situation with E. coli, 46 only a slight increase was observed in the peptidoglycan synthesized in the presence of mecillinam compared with that obtained from untreated cells (32.8% and 28.4%, respectively). Likewise, a similar level of 29.5% cross-linking was present in the peptidoglycan from the PAO1 DpbpA mutant.…”

Beta‐lactam antibiotics: from antibiosis to resistance and bacteriology

“… Inactivation of PBP2 resulted in a doubling of the E. coli cell wall anhydromuramic acid content, thus implicating PBP in cell wall glycan chain length regulation (97). In the presence of cefsulodin and cefmetazole, cephalosporins that bind to all PBPs but PBP2, the murein synthesized acquired a degree of cross‐linkage even higher than the control cells, demonstrating that PBP2, or other proteins, might have a transpeptidase activity in vivo able to produce a highly cross‐linked peptidoglycan (95).…”

“…Inactivation of PBP2 resulted in a doubling of the E. coli cell wall anhydromuramic acid content, thus implicating PBP in cell wall glycan chain length regulation (97).…”

Cell cycle parameters of Proteus mirabilis: interdependence of the biosynthetic cell cycle and the interdivision cycle

“…Thus, mecillinam allowed us to determine the time of initiation of sacculus elongation, i.e., the start of a new period of murein biosynthesis within the interdivision cycle. However, perturbation of murein sacculus elongation in progress by mecillinam did not seem to affect division, despite the fact that mecillinam treatment yields altered murein in E. coli (6) as well as in P. mirabilis (E. Sarnow and J. Gmeiner, manuscript in preparation). In this regard, it is interesting to note that synchronized cells of P. mirabilis, cultivated in the presence of mecillinam in complex medium, regained division capability after about 180 min, although synchrony was lost (data not shown).…”