Jeudi 12 avril 2012 à 11h30

Pr. Melanie BLOCKESCH

Laboratory of Molecular Microbiologie
École polytechnique fédérale de Lausanne, Switzerland

"Love" in the Time of Cholera – Horizontal gene transfer between Vibrio cholerae strains

Invitée par François-Xavier Barre (01 69 82 32 24)

Résumé

The etiological agent of the disease cholera, Vibrio cholerae, is an aquatic bacterium often encountered in rivers, estuaries and coastal regions. Within this environmental niche, the bacterium often associates with the chitinous exoskeleton of zooplankton. Colonization of such chitin surfaces triggers the onset of a developmental program known as natural competence for transformation.
We studied the regulatory network of this mode of horizontal gene transfer in great detail and discovered that at least three interconnected signaling cascades are required for competence induction. These signaling pathways are based on bacterial metabolism, carbon catabolite repression, and group behavior.

Jeudi 8 mars 2012 à 11h30

Pr. Judith ARMITAGE

Oxford Centre for Integrative Systems Biology
Department of Biochemistry - University of Oxford

How do bacteria know where to go? Rotary motors and protein dynamics drive bacterial behaviour

Invitée par François-Xavier Barre (01 69 82 32 24)

Résumé

Bacteria swim by rotating helical flagella using the movement of ions through transmembrane rings of proteins to drive rotation at speeds of up to 1500Hz. The switching frequency of the motors from counter clockwise to clockwise is controlled by a sensory system, and biases the swimming direction to an optimum environment for growth. Chemosensory regulated swimming is a major factor in virulence, biofilm formation and environmental cycling.
Using a combination of molecular genetics, biochemistry, biophysics, structural biology, in vivo imaging and modelling we have identified unexpected mechanisms localising proteins within bacterial cell, ensuring balanced sensory signalling, and shown that the flagellar motor is not the simple "electric motor" described in text books.

Mercredi 7 mars 2012 à 11h30

Robert DRILLIEN

Institut de Génétique et de Biologie Moléculaire et Cellulaire
INSERM U596 / CNRS - UMR7104, Illkirch

Vaccinia virus overexpression of proteins in mammalian cells for fonctional and structural studies

Invité par Georges Beaud (01 69 82 31 49)

Résumé

Viruses are well suited as vectors for high level expression of proteins in mammalian cells. We have developed an expression system based on a strain of vaccinia virus (modified vaccinia virus Ankara, MVA) that is safe for laboratory workers and can be handled under BSL1 containment. Vaccinia recombinants were designed to encode the bacteriophage T7 RNA polymerase under the control of a vaccinia promoter and E.coli lac operator while the gene of interest is under the control of a phage T7 promoter and lac operator.
Recombinant virus construction is carried out in the absence of foreign protein expression which is turned on by adding the inducer IPTG. Using this procedure protein expression can be as high as 15mg for 108 cells and a single protein species can be purified to mg levels from a few liters of cell culture. To simplify gene cloning we have devised specialized plasmids that add one of a series of purification tags at the N-terminus of the gene of interest and enable straightforward Gateway recombination to create the plasmid needed for isolation of recombinant viruses. Protein expression is carried out in suspension cell cultures grown in orbital shakers. Current improvements are being attempted to accelerate the process of recombinant virus isolation.
So far about 10 different full length mammalian proteins have been successfully expressed, some in instances where E. coli or baculovirus expression failed. Several examples of protein expression, purification, biochemical and biophysical characterization will be illustrated (HIV integrase, tubulin tyrosine ligase-like 12).

Mardi 6 mars 2012 à 14h30

Salle de conférences du Centre de Génétique Moléculaire
Bâtiment 23-24, CNRS Gif-sur-Yvette

Soufian OUCHANE

Biogenèse des complexes bioénergétiques et formation du biofilm chez Rubrivivax gelatinosus :
effet de l’oxygène, la lumière et le cuivre 

Soutenance d'Habilitation à Diriger des Recherches - Université Paris-Sud 11

Jeudi 16 février 2012 à 11h30

Peter MERGAERT

Institut des Sciences du Végétal, CNRS, Gif-sur-Yvette

titre en attente

Invité par Frédéric Boccard (01 69 82 32 20)

Résumé

.