Recombinational instability of F′ plasmids in Escherichia coli K-12

✍ Scribed by Bresler, S. E. ;Krivonogov, S. V. ;Lanzov, V. A.

• Publisher: Springer
• Year: 1981
• Tongue: English
• Weight: 493 KB
• Volume: 183
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00270161

✦ Synopsis

The F' plasmids ORF-1 (purE+ tsxs proC+ lac+) and F'14 (argE+ metB+ ilv+) contain active regions of recombination, fre I and fre II correspondingly. The plasmid ORF-1 is stable in recF- cells (i.e., with the RecBC pathway of recombination) and decays in rec+ cells (RecBCF pathway) giving two types of product: F+ and plasmid pCK-1 (tsxs proC+ lac+) containing part of the initial DNA. They are extremely instable in the presence of the RecF pathway, (recBC- sbcB-), yielding F+ and plasmid pCK-2 (proC+ lac+). The instability of plasmids depends on a region of homology between the chromosome and the episome. The instability of ORF-1 shows the participation of IS3 elements (alpha 1 beta 3 and alpha 3 beta 1) in the recA, recF-dependent recombinational decay and allows localization of two active sites on the chromosome: fre I1 between purE and tsx markers and fre I2 between tsx and proC. The plasmid F'14, in accordance with published data, is able to yield F+ cells by recA-independent recombination. But eventually this plasmid may undergo a recA, recF-dependent decay. Genetic analysis of these events allows localization of an active point of recombination, freII1, between argE and metB. Another active point is localized inside the F factor. The recA-dependent decay of plasmid F-14 is also excluded on the RecBC pathway (recF- strains).