Anne M E Gasc

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Penicillin resistance in Streptococcus pneumoniae has been attributed so far to the production of penicillin-binding protein (PBP) variants with decreased affinities for beta-lactam antibiotics. Cefotaxime-resistant laboratory mutants, selected after several steps on increasing concentrations of this beta-lactam, become deficient in transformation as well.(More)
Pulsed-field gel electrophoresis of genomic DNA was carried out on Streptococcus pneumoniae strains to determine its value in the epidemiological survey of pneumococcal infections. Twenty-one clinical strains were chosen to cover a broad range of diversity according to geographic location, penicillin susceptibility, serotype, and multilocus enzyme(More)
Pulsed-field gel electrophoresis of the genomic DNA of penicillin-resistant strains of Streptococcus pneumoniae was carried out. Eleven clinical strains of serogroup 9 from different French towns and Paris hospitals were tested. The restriction enzymes Apal and Smal were used to digest intact chromosomes, and the fragments were resolved by field-inversion(More)
A physical map of the Streptococcus (Diplococcus) pneumoniae chromosome, which is circular and 2,270 kbp in circumference, has been constructed. The restriction enzymes ApaI, SmaI, and SacII were used to digest intact chromosomes, and the fragments were resolved by field inversion gel electrophoresis (FIGE). The digests produced 22, 20, and 29 fragments,(More)
A mutation in the ciaH gene of Streptococcus pneumoniae induces cefotaxime resistance and transformation deficiency. ciaH encodes a putative sensor protein that belongs to the family of signal-transducing histidine kinases. This gene is adjacent to ciaR, which encodes a DNA-binding protein involved in the regulation of genes responding to environmental(More)
The use as genetic markers, during transformation of Streptococcus pneumoniae, of 19 sequences differing from wild type, located throughout the amiA locus, enabled us to examine the fate of 24 single- and 11 multiple-mismatches during recombination. Tentative mismatch ranking as a function of decreasing repair efficiency by the Hex mismatch repair system is(More)
The dnaA gene region of Streptococcus pneumoniae was cloned and sequenced. A tRNA gene, seven ORFs and three DnaA box clusters were identified. The order of the genes and intergene regions found was tRNA(Arg)-orf1-DnaA box cluster 3-htrA-spoOJ-DnaA box cluster 2-dnaA-DnaA box cluster 1-dnaN-orfX-orfY. Five ORFs are homologous to known bacterial genes. The(More)
Genetic transformation in Streptococcus pneumoniae involves the insertion of single-stranded pieces of donor DNA into a recipient genome. Efficiencies of transformation strongly depend on the mutations (markers) carried by donor DNA. Markers are classified according to their transforming efficiencies into very high, high, intermediate, and low efficiency.(More)
In pneumococcal transformation, recombination frequency between point mutations is usually proportional to physical distances. We have identified an aberrant marker belonging to the amiA locus that appeared to markedly enhance recombination frequency when crossed with any other markers of this gene. This mutation results from the C-to-A transversion in the(More)
In pneumococcal transformation a particular point mutation belonging to the amiA locus is able markedly to enhance recombination frequency when crossed with any other markers of this gene. This results from a polarized conversion of the mutation towards the wild-type sequence. In this report, by site-directed oligonucleotide mutagenesis, we have generated a(More)