Programme des séminaires de Juin-Juillet 2014

Département de Microbiologie,
Institut Pasteur, 25 rue du Dr Roux - 75015 Paris

. vendredi 6 juin 2014, 11:30 : Melissa CAIMANO (University of Connecticut, USA)

. vendredi 20 juin 2014, 11:30 : Laurent DEBARBIEUX (BMGE, Institut Pasteur, Paris)

. vendredi 27 juin 2014, 11:30 : Ashlee EARL (The Broad Institute of MIT & Harvard, USA)


. Lundi 30 juin et mardi 1er juillet 2014, 9:00 : Journées du Département de Microbiologie (Institut Pasteur)


. jeudi 3, juillet 2014, 14:00 : Christian DEMEURE (The Broad Institute of MIT & Harvard, USA)


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Visitors have to present an identity document at the Welcome desk.




Séminaire organisé par le Département de Microbiologie


Departments of Medicine, Pediatrics and Molecular & Structural Biology

University of Connecticut (USA)


Environmental sensing by Borrelia burgdorferi : How do Lyme disease spirochetes know if they are coming or going ?

vendredi 6 juin 2014 à 11 h 30
salle Jean-Paul Aubert - RdC Bâtiment Fernbach

contact : Mathieu Picardeau (

Following acquisition from an infected mammalian host during the larval blood meal, B. burgdorferi (Bb) must adhere to rapidly differentiating midgut epithelial cells, resist deleterious substances within the lumen, and alter its metabolic machinery to utilize alternative carbon sources. During transmission, spirochetes presumably must cope with these same blood meal-associated stressors, while traversing the midgut and salivary glands in order to gain access to the mammalian host. A major conundrum in Lyme disease research is how acquisition and transmission can elicit ostensibly similar protective/physiologic adaptations, yet evoke markedly different spirochete behaviors. Spirochetes lacking the alternative  sigma-factor RpoS are impaired in network formation, the initial non-motile of phase of biphasic dissemination. Using site-directed and Tn-mediated mutagenesis, we now have identified at least 9 RpoS-upregulated genes involved in infection via tick bite, results which collectively support our conceptualization of RpoS-dependent gene expression as a ‘Go’ signal for tick-to-mammal transmission. In contrast, spirochetes within acquiring ticks remain associated predominantly with the luminal surfaces of the midgut and, importantly, do not form networks. Bb within feeding larvae are in an RpoS-OFF state, thereby allowing for de-repression of ospA, the prototypical tick-phase borrelial gene. OspA-deficient Bb survive the larval blood meal, but do not persist through the molt, enabling us to conclude that the RpoS-OFF state contributes to the induction of a tick-adaptive ‘Stay’ signal. Spirochetes lacking the Hk1/Rrp1 two-component system (TCS), which signals via synthesis of c-di-GMP, are destroyed within the midguts of feeding larvae. Structural modeling of the Hk1 periplasmic sensor points to tick- and/or host-derived neurotransmitters as potential activating ligands. Side-by-side comparison of delta-hk1, delta-rrp1, and delta-glp Bb revealed that Hk1/Rrp1-dependent gene products aside from those involved in glycerol uptake and utilization are required to counter noxious substances associated with tick-feeding; we postulate that this occurs via remodeling of the borrelial cell envelope. The requirement for c-di-GMP signaling within feeding nymphs demonstrates that the blood meal-associated stressors that Bb encounters during acquisition also are present during transmission. In summary, the tick phase of Bb’s enzootic cycle appears to involve three distinct genetic programs: RpoS-ON, RpoS-OFF and Hk1/Rrp1-ON, which provide Go, Stay, and bloodmeal-survival signals, respectively.




Institut Pasteur, Unité BMGE, Groupe IBBA

'The Great Come Back of Therapeutic Bacteriophages: why and how'

vendredi 20 juin 2014 à 11 h 30
salle Jean-Paul Aubert – RdC Bâtiment Fernbach

contact : Jean-Marc Gigo /


Today, everyone, anywhere, can be infected by multidrug resistant (MDR) bacteria. The hope for the discovery of new antibiotics has lasted 25 years without any major breakthrough. In this context, research on bacteriophages, the natural biological enemies of bacteria have been reignited. Despite an early development started 100 years ago, therapeutic use of bacteriophages, Phage Therapy, will not again be considered as a medical treatment, without experimental data demonstrating its efficacy in treating MDR infections.

The past few years, we have acquired data, using various animal models, which support treatments for both pulmonary and gut infections. More recently, we started to delineate some limits on the medical use of bacteriophages. We are also investigating fundamental questions on the relationships between bacteriophages and bacteria in complex ecosystems. How do mammalians cells, bacteria and bacteriophages interact with each others remains an open question.



Ashlee EARL

Bacterial Genomics Genome Sequencing & Analysis Program, The Broad Institute of MIT & Harvard (Cambridge USA)

'Genomic Studies of Bacterial Pathogen Evolution and Drug Resistance'

vendredi 27 juin 2014 à 11 h 30

salle Jean-Paul Aubert – RdC Bâtiment Fernbach

contact : Patrice Courvalin /

Abstract :

New sequencing technologies are providing extraordinary opportunities to tackle longstanding and emerging challenges in infectious disease. Capitalizing on these technologies requires thoughtful study design, access to appropriate samples, metadata, and development of suitable analytical approaches. The emergence of multidrug resistant strains of pathogens has become a leading public health concern. To address this concern, we have developed new approaches and tools to examine drug resistant Mycobacterium tuberculosis, and to study the emergence of multidrug resistant strains of enterococci as leading causes of hospital acquired infection. These tools include new algorithms for identifying sequence polymorphisms and adapting existing algorithms for the very large data sets that are now being produced by next generation sequencing. In close partnership with our collaborators, we sequenced and applied these tools to the analysis of genomes from large sets of well-characterized strains of mycobacteria and enterococci. Among our findings with M. tuberculosis, we identified harbinger mutations of multidrug resistance that may inform new strategies for preempting emergence of successive resistance. With enterococci, we have found that vancomycin resistant Enterococcus faecium evolved as the result of anthropogenic forces over the past 5,000 years, and that there is substantial diversity in gene content within this genus. I will discuss our findings as well as the development of analytical approaches that take into account the unique features and distinct evolutionary history of each species’ genome.



Journées du Département de Microbiologie

Lundi 30 juin - 1er juillet 2014

Auditorium - CIS - Institut Pasteur

Comité d'organisation : C. Beloin, H. De Reuse, J.-M. Ghigo, C. Le Bouguenec, P. Trieu-Cuot

Contact : ana.cova-rodrigues at


Programme (PDF)




Soutenance Habilitation à Diriger des Recherches

Université Paris Descartes


Christian DEMEURE

Unité de recherche Yersinia dirigée par Elisabeth Carniel - Département de Microbiologie


Immunité innée et adaptative contre Yersinia pestis, agent de la peste.


jeudi 3 juillet 2014 à 14 h 00

salle Jules Bordet – rdc Bâtiment Metchnikoff

contact : Christian Demeure (

Mis à jour le 27/06/2014


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