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Appl. Environ. Microbiol., Oct 1996, 3727-3731, Vol 62, No. 10
JT Singer, C Ma and KJ Boettcher
A defect in generalized recombination has prevented the use of marker
exchange for the construction of specific chromosomal mutations in the
marine fish pathogen Vibrio anguillarum 775. Through the use of large
segments of homologous DNA, we were successful in overcoming this defect
and used marker exchange to construct a recA mutant of V. anguillarum
H775-3. A recombinant cosmid carrying the recA gene of V. anguillarum 775
in the center of a 25-kb cloned DNA insert was isolated by complementation
of methyl methanesulfonate (MMS) sensitivity in Escherichia coli HB101. The
recA gene was inactivated by inserting a kanamycin resistance gene into
recA, and the mutant gene was subsequently introduced into V. anguillarum
H775-3 by conjugal mobilization. Isolation of recombinants between
cosmid-borne recA::kan sequences and chromosomal DNA was facilitated by the
introduction of an incompatible plasmid, and Southern hybridization was
used to verify the presence of recA::kan in the chromosomal DNA of the recA
mutant. V. anguillarum carrying recA::kan was considerably more sensitive
to UV radiation and to MMS than was its parent, and near wild-type levels
of resistance to MMS and UV light were restored by introduction of cloned
recA genes from both E. coli and V. anguillarum. These results indicate
that recA is required for DNA repair in V. anguillarum and demonstrate the
utility of this modified marker exchange technique for the construction of
mutations in this economically important fish pathogen.
Copyright © 1996, American Society for Microbiology
Overcoming a defect in generalized recombination in the marine fish pathogen Vibrio anguillarum 775: construction of a recA mutant by marker exchange
Department of Biochemistry, Microbiology and Molecular Biology, University of Maine, Orono 04469-5735, USA. jsinger@maine.maine.edu
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