Lucie Chenu | Université Paul Sabatier de Toulouse (original) (raw)

Papers by Lucie Chenu

Research paper thumbnail of Rôle de la protéine de liaison à la pénicilline 3 (PBP 3) de Streptococcus pneumoniae dans la physiologie de cet organisme et sa résistance au céfotaxime

Le but de cette these est d'etudier les genes de resistance aux beta-lactamines chez streptoc... more Le but de cette these est d'etudier les genes de resistance aux beta-lactamines chez streptococcus pneumoniae, en particulier le role de la proteine de liaison a la penicilline 3 (pbp 3). Nous avons montre que cette proteine protege les bacteries contre des exces de glycine et de d-amino acides ainsi que contre un exces de chaleur. Puis, nous avons transforme des souches sensibles, a contenu normal ou non en pbp 3, par l'adn de la souche tres resistante au cefotaxime. Trois genes au moins sont impliques dans cette resistance. La mutation de l'un d'entre eux provoque un blocage complet de la transformation du pneumocoque. Nous avons montre que la transformation par un plasmide est possible par electroporation, c'est donc la penetration de l'adn qui est affectee. Nous avons etudie l'effet de la pbp 3 sur la resistance au cefotaxime en introduisant le gene codant pour la quantite normale de pbp 3 dans diverses souches resistantes. La comparaison des souches ...

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Research paper thumbnail of Genetic studies of cefotaxime resistance in Streptococcus pneumoniae: relationship to transformation deficiency

Research in Microbiology, 1993

A laboratory pneumococcal strain resistant to cefotaxime was studied by DNA-induced transformatio... more A laboratory pneumococcal strain resistant to cefotaxime was studied by DNA-induced transformation in order to characterize its genetic structure. At least three independent genes were required to confer the highest level of resistance to this beta-lactam antibiotic. The accumulation of mutations in these three genes accounted for three levels of resistance. Mutation of the gene encoding penicillin-binding protein 2x was very likely responsible for the first step of resistance, which was a prerequisite for sequential increase in resistance. Additionally, strains highly resistant to cefotaxime were defective for natural transformation. Revertants of these strains were frequently observed. Such strains had recovered full transformability, suggesting a correlation between the inability to be transformed and a high level of resistance to cefotaxime. The possibility of electrotransforming these highly resistant strains suggests that natural transformation is probably blocked at the DNA-uptake level.

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Research paper thumbnail of Molecular Characterization of a Mutation Affecting the Amount of Streptococcus pneumoniae Penicillin-Binding Protein 3

Microbial Drug Resistance, 1997

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Research paper thumbnail of Genetic studies of cefotaxime resistance in Streptococcus pneumoniae: relationship to transformation deficiency

Research in Microbiology, 1993

A laboratory pneumococcal strain resistant to cefotaxime was studied by DNA-induced transformatio... more A laboratory pneumococcal strain resistant to cefotaxime was studied by DNA-induced transformation in order to characterize its genetic structure. At least three independent genes were required to confer the highest level of resistance to this beta-lactam antibiotic. The accumulation of mutations in these three genes accounted for three levels of resistance. Mutation of the gene encoding penicillin-binding protein 2x was very likely responsible for the first step of resistance, which was a prerequisite for sequential increase in resistance. Additionally, strains highly resistant to cefotaxime were defective for natural transformation. Revertants of these strains were frequently observed. Such strains had recovered full transformability, suggesting a correlation between the inability to be transformed and a high level of resistance to cefotaxime. The possibility of electrotransforming these highly resistant strains suggests that natural transformation is probably blocked at the DNA-uptake level.

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Research paper thumbnail of Il était une nouvelle fois -- préface de l'anthologie Contes de Villes et de Fusées

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Research paper thumbnail of préface de l'anthologie Et d'Avalon à Camelot

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Research paper thumbnail of préface de l'anthologie De Brocéliande en Avalon

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Research paper thumbnail of Carte d'Identités ou "dis-moi qui tu hais, je te dirais qui tu es" -- préface de l'anthologie Identités

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Research paper thumbnail of Gestation -- préface de l'anthologie (Pro)Créations

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Research paper thumbnail of Rôle de la protéine de liaison à la pénicilline 3 (PBP 3) de Streptococcus pneumoniae dans la physiologie de cet organisme et sa résistance au céfotaxime (Thèse)

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Research paper thumbnail of TOLKIEN JOHN RONALD REUEL (1892-1973)

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Research paper thumbnail of ASIMOV ISAAC (1920-1992)

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Research paper thumbnail of Molecular Characterization of a Mutation Affecting the Amount of Streptococcus pneumoniae Penicillin-Binding Protein 3

Microbial Drug Resistance, 1997

We have studied the molecular structure of the gene for the penicillin binding protein (PBP 3) of... more We have studied the molecular structure of the gene for the penicillin binding protein (PBP 3) of the Streptococcus pneumoniae wild-type strain and a laboratory mutant strain that exhibits a reduced amount of this protein on PBP gels. This mutation affects cefotaxime resistance when transferred into resistant strains. We have sequenced the PBP3 gene, dacA, and upstream regions from the wild-type isogenic strain and the laboratory mutant. We show that a deletion of one base-pair in the upstream sequence of this gene account for the phenotype by decreasing the amount of PBP3.

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Research paper thumbnail of The role of penicillin-binding protein 3 (PBP 3) in cefotaxime resistance in Streptococcus pneumoniae

Molecular and General Genetics, 1993

A pneumococcal strain, with a reduced amount of penicillin-binding protein 3 (PBP 3), permitted a... more A pneumococcal strain, with a reduced amount of penicillin-binding protein 3 (PBP 3), permitted an analysis of the role of this protein in cefotaxime resistance. We observed that reduced amounts of PBP 3 sensitize the bacteria to high temperature, to excess glycine and to some D-amino acids. These phenotypes suggest that the amount of PBP 3 may influence the membrane properties of the bacteria. The strain with reduced PBP 3 was transformed to cefotaxime resistance. We show that the PBP 3 mutation, in certain genetic backgrounds, decreases the level of resistance to cefotaxime by a factor of 2. Models are presented to explain this result.

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Research paper thumbnail of Rôle de la protéine de liaison à la pénicilline 3 (PBP 3) de Streptococcus pneumoniae dans la physiologie de cet organisme et sa résistance au céfotaxime

Le but de cette these est d'etudier les genes de resistance aux beta-lactamines chez streptoc... more Le but de cette these est d'etudier les genes de resistance aux beta-lactamines chez streptococcus pneumoniae, en particulier le role de la proteine de liaison a la penicilline 3 (pbp 3). Nous avons montre que cette proteine protege les bacteries contre des exces de glycine et de d-amino acides ainsi que contre un exces de chaleur. Puis, nous avons transforme des souches sensibles, a contenu normal ou non en pbp 3, par l'adn de la souche tres resistante au cefotaxime. Trois genes au moins sont impliques dans cette resistance. La mutation de l'un d'entre eux provoque un blocage complet de la transformation du pneumocoque. Nous avons montre que la transformation par un plasmide est possible par electroporation, c'est donc la penetration de l'adn qui est affectee. Nous avons etudie l'effet de la pbp 3 sur la resistance au cefotaxime en introduisant le gene codant pour la quantite normale de pbp 3 dans diverses souches resistantes. La comparaison des souches ...

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Research paper thumbnail of Genetic studies of cefotaxime resistance in Streptococcus pneumoniae: relationship to transformation deficiency

Research in Microbiology, 1993

A laboratory pneumococcal strain resistant to cefotaxime was studied by DNA-induced transformatio... more A laboratory pneumococcal strain resistant to cefotaxime was studied by DNA-induced transformation in order to characterize its genetic structure. At least three independent genes were required to confer the highest level of resistance to this beta-lactam antibiotic. The accumulation of mutations in these three genes accounted for three levels of resistance. Mutation of the gene encoding penicillin-binding protein 2x was very likely responsible for the first step of resistance, which was a prerequisite for sequential increase in resistance. Additionally, strains highly resistant to cefotaxime were defective for natural transformation. Revertants of these strains were frequently observed. Such strains had recovered full transformability, suggesting a correlation between the inability to be transformed and a high level of resistance to cefotaxime. The possibility of electrotransforming these highly resistant strains suggests that natural transformation is probably blocked at the DNA-uptake level.

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Research paper thumbnail of Molecular Characterization of a Mutation Affecting the Amount of Streptococcus pneumoniae Penicillin-Binding Protein 3

Microbial Drug Resistance, 1997

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Research paper thumbnail of Genetic studies of cefotaxime resistance in Streptococcus pneumoniae: relationship to transformation deficiency

Research in Microbiology, 1993

A laboratory pneumococcal strain resistant to cefotaxime was studied by DNA-induced transformatio... more A laboratory pneumococcal strain resistant to cefotaxime was studied by DNA-induced transformation in order to characterize its genetic structure. At least three independent genes were required to confer the highest level of resistance to this beta-lactam antibiotic. The accumulation of mutations in these three genes accounted for three levels of resistance. Mutation of the gene encoding penicillin-binding protein 2x was very likely responsible for the first step of resistance, which was a prerequisite for sequential increase in resistance. Additionally, strains highly resistant to cefotaxime were defective for natural transformation. Revertants of these strains were frequently observed. Such strains had recovered full transformability, suggesting a correlation between the inability to be transformed and a high level of resistance to cefotaxime. The possibility of electrotransforming these highly resistant strains suggests that natural transformation is probably blocked at the DNA-uptake level.

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Research paper thumbnail of Il était une nouvelle fois -- préface de l'anthologie Contes de Villes et de Fusées

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Research paper thumbnail of préface de l'anthologie Et d'Avalon à Camelot

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Research paper thumbnail of préface de l'anthologie De Brocéliande en Avalon

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Research paper thumbnail of Carte d'Identités ou "dis-moi qui tu hais, je te dirais qui tu es" -- préface de l'anthologie Identités

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Research paper thumbnail of Gestation -- préface de l'anthologie (Pro)Créations

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Research paper thumbnail of Rôle de la protéine de liaison à la pénicilline 3 (PBP 3) de Streptococcus pneumoniae dans la physiologie de cet organisme et sa résistance au céfotaxime (Thèse)

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Research paper thumbnail of TOLKIEN JOHN RONALD REUEL (1892-1973)

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Research paper thumbnail of ASIMOV ISAAC (1920-1992)

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Research paper thumbnail of Molecular Characterization of a Mutation Affecting the Amount of Streptococcus pneumoniae Penicillin-Binding Protein 3

Microbial Drug Resistance, 1997

We have studied the molecular structure of the gene for the penicillin binding protein (PBP 3) of... more We have studied the molecular structure of the gene for the penicillin binding protein (PBP 3) of the Streptococcus pneumoniae wild-type strain and a laboratory mutant strain that exhibits a reduced amount of this protein on PBP gels. This mutation affects cefotaxime resistance when transferred into resistant strains. We have sequenced the PBP3 gene, dacA, and upstream regions from the wild-type isogenic strain and the laboratory mutant. We show that a deletion of one base-pair in the upstream sequence of this gene account for the phenotype by decreasing the amount of PBP3.

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Research paper thumbnail of The role of penicillin-binding protein 3 (PBP 3) in cefotaxime resistance in Streptococcus pneumoniae

Molecular and General Genetics, 1993

A pneumococcal strain, with a reduced amount of penicillin-binding protein 3 (PBP 3), permitted a... more A pneumococcal strain, with a reduced amount of penicillin-binding protein 3 (PBP 3), permitted an analysis of the role of this protein in cefotaxime resistance. We observed that reduced amounts of PBP 3 sensitize the bacteria to high temperature, to excess glycine and to some D-amino acids. These phenotypes suggest that the amount of PBP 3 may influence the membrane properties of the bacteria. The strain with reduced PBP 3 was transformed to cefotaxime resistance. We show that the PBP 3 mutation, in certain genetic backgrounds, decreases the level of resistance to cefotaxime by a factor of 2. Models are presented to explain this result.

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