Publication Date:
2012-03-20
Description:
Background The R6K replicon is one of the best studied bacterial plasmid replicons. Replication of the R6K plasmid and derivatives harboring its γ origin of replication (ori R6Kγ) is dependent on the pir gene-encoded π protein. Originally encoded by R6K, this protein is usually provided in trans in hosts engineered to support replication of plasmids harboring ori R6Kγ. In Escherichia coli this is commonly achieved by chromosomal integration of pir either via lysogenization with a λpir phage or homologous recombination at a pre-determined locus. Findings Current methods for construction of host strains for ori R6Kγ-containing plasmids involve procedures that do not allow selection for presence of the pir gene and require cumbersome and time-consuming screening steps. In this study, we established a mini-Tn7-based method for rapid and reliable construction of pir + host strains. Using a curable mini-Tn7 delivery plasmid, pir expressing derivatives of several commonly used E. coli cloning and mobilizer strains were isolated using both the wild-type pir + gene as well as the copy-up pir-116 allele. In addition, we isolated pir + and pir-116 expressing derivatives of a clinical isolate of Salmonella enterica serovar Typhimurium. In both E. coli and S. enterica serovar Typhimurium, the presence of the pir + wild-type or pir-116 alleles allowed the replication of ori R6Kγ-containing plasmids. Conclusions A mini-Tn7 system was employed for rapid and reliable engineering of E. coli and S. enterica serovar Typhimurium host strains for plasmids containing ori R6Kγ. Since mini-Tn7 elements transpose in most, if not all, Gram negative bacteria, we anticipate that with relatively minor modifications this newly established method will for the first time allow engineering of other bacterial species to enable replication of plasmids with ori R6Kγ.
Electronic ISSN:
1756-0500
Topics:
Biology
,
Medicine
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