Mitomycin-C-induced changes in the nucleoid of Escherichia coli K12.
The influence of low concentrations of mitomycin-C on the structure of the envelope-free nucleoid was studied in several strains of Escherichia coli K12. The wild-type strain AB1157 uvr+ rec+ and 3 mitomycin-C-sensitive derivatives carrying mutations in the uvrA, uvrB and recA genes, were used. Treatment of the control strain with mitomycin-C, 0.5 microgram/ml, followed by incubation in drug-free medium resulted in the formation of a transient fast-sedimenting nucleoid with a sedimentation coefficient of 2200 S. A fraction of 25% of the nucleoids had attained the normal sedimentation coefficient of 1570 S 3 h after removal of mitomycin-C. With the uvr- strains, mitomycin-C induced a slow, almost linear increase in the S value of the envelope-free nucleoid. In these cases the S value continued to increase during post-incubation and was 2050 S 3 h after removal of the drug. Post-incubation of recA- cells resulted in loss of supercoiling, decrease in S value of the nucleoid and degradation of DNA. Results obtained with phase-contrast and electron microscopy were in good agreement with the hydrodynamic data.
D004260:DNA Repair; D004279:DNA, Viral / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects* / Q000648:ultrastructure; D008854:Microscopy, Electron; D008858:Microscopy, Phase-Contrast; D016685:Mitomycin; D008937:Mitomycins / Q000494:pharmacology*; D014461:Ultracentrifugation
D004279:DNA, Viral; D008937:Mitomycins; D016685:Mitomycin