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.