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Appl. Environ. Microbiol., Sep 1997, 3539-3547, Vol 63, No. 9
PE Framson, A Nittayajarn, J Merry, P Youngman and CE Rubens
Three techniques were developed to improve the genetic manipulation of
group B streptococci (GBS). We first optimized a protocol for
transformation of GBS by electroporation, which provided transformation
efficiencies of 10(5) CFU/microgram. Variables that influenced the
transformation efficiency were the glycine content of the competent cell
growth media, the electric field strength during electroporation, the
electroporation buffer composition, the host origin of the transforming
plasmid, and the concentration of selective antibiotic at the final
plating. Our transformation protocol provides an efficiency sufficient for
cloning from ligation reactions directly into GBS, obviating an
intermediate host such as Escherichia coli. Second, temperature-sensitive
plasmids of the pWV01 lineage were shown to transform GBS, and their
temperature-sensitive replication was confirmed. Lastly, the
temperature-sensitive pWV01 plasmid pTV1OK, which contains Tn917, was used
as a transposon delivery vector for the construction of genomic Tn917
mutant libraries. We have shown, for the first time, that Tn917 transposes
to the GBS chromosome and at a frequency of 10(-3)/CFU. Furthermore,
representative clones from a Tn917 library contained single transposon
insertions that were randomly located throughout the chromosome. These
techniques should provide useful methods for cloning, mutagenesis, and
characterization of genes from GBS.
Copyright © 1997, American Society for Microbiology
New genetic techniques for group B streptococci: high-efficiency transformation, maintenance of temperature-sensitive pWV01 plasmids, and mutagenesis with Tn917
Virginia Mason Research Center, University of Washington, Seattle, USA.
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