Genetic analysis of maintenance of pEC156, a naturally occurring Escherichia coli plasmid that carries genes of the EcoVIII restriction–modification system

Publication date: Available online 8 December 2014 Source:Plasmid Author(s): Olesia Werbowy , Robert Boratynski , Agnieszka Dekowska , Tadeusz Kaczorowski In the present study the role of the mechanisms responsible for maintenance of a natural plasmid pEC156, that carries genes of the EcoVIII restriction–modification system was investigated. Analysis of this plasmid's genetic content revealed the presence of genetic determinants suggesting two such mechanisms. The first of them relies on site specific recombination utilizing the Xer/cer molecular machinery, while the second involves a restriction–modification system as an addiction module. Our analysis indicated that three factors affect the maintenance of pEC156: (i) a cis-acting cer site involved in resolution of plasmid multimers, (ii) a gene coding for EcoVIII endonuclease, and (iii) plasmid copy number control. The lowest stability was observed with pEC156 derivatives deprived of the cer site. Decreased stability of pEC156 derivatives was also observed in E. coli strains deficient in genes coding for proteins involved in plasmid multimer resolution (XerC, XerD, ArgR and PepA). A similar effect, but to a much lesser extent was observed for the pEC156 derivative without a functional gene coding for EcoVIII endonuclease. Our results indicate that the presence of the cer site is more important for pEC156 stable maintenance than the presence of a functional gene coding for EcoVIII endonuclease. In our work we al...
Source: Plasmid - Category: Biotechnology Source Type: research