Inhibition of Envelope Polymerizations in Filamentous Escherichia coli B

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

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.

Bacterial cell division regulation: physiological effects of crystal violet on Escherichia coli lon + and lon - strains

The Escherichia coli lon(-) mutants apparently are defective in the ability to recommence cell division after temporary periods of deoxyribonucleic acid (DNA) synthesis inhibition. They are also more susceptible to cell division inhibition by the basic dye, crystal violet (CV), than are lon(+) strains. In enriched broth, the lon(+) strain continued to grow and divide in the presence of CV, but lon(-) cell division was inhibited and filamentous growth resulted. In a supplemented minimal medium containing CV, lon(-) cell division was only temporarily inhibited. There was no detectable specific effect on DNA synthesis, although CV slowed the rate of mass increase in both media. Trichloroacetic acid-insoluble lipid synthesis was preferentially inhibited in both lon(+) and lon(-) strains. In CV-containing enriched broth, diaminopimelic acid incorporation into trichloroacetic acid-insoluble compounds occurred at a rate greater than the rate of mass increase in both lon(+) and lon(-) strains. In a CV-containing supplemented minimal medium, diaminopimelic acid was incorporated to a greater extent by lon(-) cells than by lon(+) cells.

Incorporation of 5-diazouracil-2-14C into ribonucleic acids of Escherichia coli during division inhibition

Radioactive diazouracil (DZU-2-(14)C) was rapidly incorporated into acid-insoluble material of Escherichia coli B. Isolated ribonucleic acid contained essentially all of the incorporated label, and this was solubilized by ribonucleases but not by deoxyribonuclease. A maximum of 45 to 50% of added label was incorporated at division-inhibitory and subinhibitory concentrations. Incorporation levels and filament-forming capacity were concomitantly depressed by preincubation of DZU in various medium components. The lower levels of incorporation brought about by preincubation were apparently related to an inherent instability or high reactivity of the DZU. The limit on incorporation of fresh DZU suggests the presence of geometrical isomers in the original DZU. The nature of these isomers and the reactivity of DZU are discussed in relation to its use in future cell division studies.