title: Mutants of the mini-F plasmid pML31 thermosensitive in replication.
abstract: Hydroxylamine mutagenesis was used for the induction of thermosensitive replication mutants of the mini-F plasmid pML31. Replication mutants were characterized by studying the segregation kinetics and the incorporation of [3H]-thymidine into plasmid deoxyribonucleic acid at the nonpermissive temperature. Based on these experiments two types of mutants could be distinguished. Mutants of type I are fast segregating with the kinetics expected if plasmid replication was blocked immediately. Double-label experiments showed a rapid shut-off of replication in these mutants at 42 degrees C. Mutants of type II segregate slower, showing only a partial inhibition of plasmid deoxyribonucleic acid synthesis at the nonpermissive temperature. The label incorporated at 42 degrees C was predominantly found in open circular plasmid molecules.
mesh_terms: D004261:DNA Replication; D004269:DNA, Bacterial / Q000096:biosynthesis*; D004270:DNA, Circular / Q000096:biosynthesis*; D004278:DNA, Superhelical / Q000096:biosynthesis; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D006898:Hydroxylamines; D009153:Mutagens; D009154:Mutation; D011815:R Factors; D013696:Temperature
chemical_list: D004269:DNA, Bacterial; D004270:DNA, Circular; D004278:DNA, Superhelical; D006898:Hydroxylamines; D009153:Mutagens