title: Abnormal excision and transfer of chromosomal segments by a strain of Escherichia coli K-12.
abstract: PB15 is an Hfr strain of Escherichia coli K-12. It arose from an F' strain carrying a temperature-sensitive F-gal by an event which blocked the detachment of F-gal in the normally reversible integration process. In PB15, the detachment of F-gal by a second mechanism can now be detected: this mechanism results in the excision and transfer of extended chromosomal segments which include the integrated F-gal; the excised segments are inferred to have circularized. Their excision, which is independent of the recA(+) allele, occurs at an unusually high rate during conjugation; a mutant F-initiator protein is suggested as the cause of this phenomenon. After their establishment in recipients, the enlarged F-genotes undergo further deletions of included donor genes by a process which is again recA(+)-independent. In Rec(+), but not in Rec(-), cells, a high proportion of the deleted fragments are rescued by integration into the recipient's chromosome.
mesh_terms: D000166:Acridines / Q000494:pharmacology; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D003227:Conjugation, Genetic; D003433:Crosses, Genetic; D004261:DNA Replication; D004926:Escherichia coli / Q000378:metabolism*; D005690:Galactose / Q000378:metabolism*; D005796:Genes; D008040:Genetic Linkage; D007930:Leucine / Q000096:biosynthesis; D009154:Mutation; D011392:Proline / Q000096:biosynthesis; D011995:Recombination, Genetic; D013696:Temperature; D013912:Threonine / Q000096:biosynthesis; D014994:Xylose / Q000378:metabolism
chemical_list: D000166:Acridines; D013912:Threonine; D011392:Proline; D014994:Xylose; D007930:Leucine; D005690:Galactose