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J. Bacteriol., Jan 1995, 52-58, Vol 177, No. 1
CS Kristensen, L Eberl, JM Sanchez-Romero, M Givskov, S Molin and V De Lorenzo
The multimer resolution system (mrs) of the broad-host-range plasmid RP4
has been exploited to develop a general method that permits the precise
excision of chromosomal segments in a variety of gram-negative bacteria.
The procedure is based on the site-specific recombination between two
directly repeated 140-bp resolution (res) sequences of RP4 effected by the
plasmid-borne resolvase encoded by the parA gene. The efficiency and
accuracy of the mrs system to delete portions of chromosomal DNA flanked by
res sites was monitored with hybrid mini-Tn5 transposons in which various
colored (beta-galactosidase and catechol 2,3 dioxygenase) or luminescent
(Vibrio harveyi luciferase) phenotypic markers associated to res sequences
were inserted in the chromosome of the target bacteria and exposed in vivo
to the product of the parA gene. The high frequencies of marker excision
obtained with different configurations of the parA expression system
suggested that just a few molecules of the resolvase are required to
achieve the site-specific recombination event. Transient expression of parA
from a plasmid unable to replicate in the target bacterium was instrumental
to effect differential deletions within complex hybrid transposons inserted
in the chromosome of Pseudomonas putida. This strategy permits the stable
inheritance of heterologous DNA segments virtually devoid of the sequences
used initially to select their insertion.
Copyright © 1995, American Society for Microbiology
Site-specific deletions of chromosomally located DNA segments with the multimer resolution system of broad-host-range plasmid RP4
Department of Microbiology, Technical University of Denmark, Lyngby.
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