Analysis of a DNA region from low-copy-number plasmid pYAN-1 ofSphingobium yanoikuyaeresponsible for plasmid stability

Abstract

We identified and analyzed a DNA region that is required for the stable maintenance of plasmids in the genus Sphingomonas. This DNA fragment, a 244 bp, is localized in the upstream region of the repA gene of low-copy-number small plasmid pYAN-1 (4896 bp) of Sphingobium yanoikuyae. It has four inverted repeats and one direct repeat for possible secondary structures. We were able to stabilize not only another unstable plasmid, pYAN-2, in the genus Sphingomonas, but also the unstable plasmid pSC101 without par locus in Escherichia coli. The copy-number levels between the unstable plasmid and the parental plasmid were similar, and these results suggest that the stabilization of unstable plasmids by this DNA region of pYAN-1 was not due to an increase in plasmid copy number. We concluded that the stabilization of the plasmid was due to a plasmid partition mechanism encoded by a DNA fragment of pYAN-1.

Localization of Low Copy Number Plasmid pRC4 in Replicating Rod and Non-Replicating Cocci Cells of Rhodococcus erythropolis PR4

“…R388 does not carry Par proteins and plasmid segregation follows a pilot fish mechanism where segregation is ensured by host chromosome segregation machinery [7]. In low copy number small plasmids such as in pSC101, pLS11 and pYAN-1 a cis sequence has been reported which does not encode for any protein but stabilizes unstable plasmids [8–10]. High copy number plasmids such as ColE1, on the other hand are randomly segregated and do not require a partitioning apparatus [11].…”