Three clinical isolates of Haemophilus ducreyi, representing at least two subtypes, were shown to be resistant to streptomycin and kanamycin. They also produced a beta-lactamase and chloramphenicol acetyltransferase and were resistant to tetracycline. In the three strains the resistance to both aminoglycoside antibiotics was encoded by a plasmid of ca. 4.7 kilobases which apparently did not car...

l h e human herpes simplex virus thymidine kinase type 1 gene (HSVtk) acts as a conditional lethal marker in mammalian cells. The HSVtk-encoded enzyme is able to phosphorylate certain nucleoside analogs (e.g. ganciclovir, an antiherpetic drug), thus converting them to toxic DNA replication inhibitors. l h e utility of HSVtk as a conditional negative-selection marker was explored in Arabidopsis ...

Clinical isolates of enterococci (Streptococcus faecalis) with high-level resistance to both streptomycin and kanamycin (minimal inhibitory concentration >2,000 mug/ml), and resistant to synergism with penicillin and streptomycin or kanamycin were examined for aminoglycoside-inactivating enzymes. All of the 10 strains studied had streptomycin adenylyltransferase and neomycin phosphotransferase ...

LacI gene encodes for the repressor of Lac operon. An Esherichia coli (E. coli) strain with a lacI knockout would yield cells that can constitutively express ß-galactosidase. Use of these cells can considerably reduce the use on an inducer isopropyl-ß-D-1-thiogalactoside (IPTG) and reduce the induction time. Jaeger et al (2) prepared a presumptive lacI knockout in E. coli C29 strain using a λ R...

In a previous study in which we examined the genome-wide response of Arabidopsis to the xenobiotic compound trinitrotoluene (TNT) via cDNA microarrays, we found that Atwbc19 (At3g55130) was among upregulated genes. Given the role of ABC transporters in cellular detoxification we sought to further characterize this gene. Initial characterization of mutants revealed that root growth of Atwbc19 kn...

Genetic studies in Borrelia burgdorferi have been hindered by the lack of a nonborrelial selectable marker. Currently, the only selectable marker is gyrB(r), a mutated form of the chromosomal gyrB gene that encodes the B subunit of DNA gyrase and confers resistance to the antibiotic coumermycin A(1). The utility of the coumermycin-resistant gyrB(r) gene for targeted gene disruption is limited b...

An attempt was made to knockout the Escherichia coli C29 lacI gene with a kanamycin resistance cassette isolated from the plasmid pACYC177. This process used the lambdared recombinase system to allow for homologous recombination, and subsequent insertion of the kanamycin cassette into the lacI gene. The E. coli C29 cells were initially transformed with pKD46, which contains the lambda-red recom...