Vérités scientifiques et enjeux sociaux

Le colloque « Vérités scientifiques et enjeux sociaux » a permis de nourrir une réflexion sur l’organisation des sciences en lien avec la production des preuves scientifiques et leurs modes de partage. Comment faire émerger la diversité des enjeux sociaux dans les sciences ? Comment partager plus largement la production scientifique et celle des preuves ? Les modes de production, de validation et de partage des preuves ne sont pas figés, ce qui les rend difficiles à appréhender. Les écueils et les mécanismes favorisant la fabrication de l’ignorance ont ainsi été abordés. L’interdisciplinarité, les sciences inclusives et les synthèses scientifiques collectives, thèmes évoqués lors du colloque, sont autant de pistes pour éclairer les débats publics, partager autrement les preuves et la capacité d’expertise, et définir collectivement les enjeux

Characterization of Vibrio Isolates from Carpet Shell Clam (Ruditapes Decussatus) Suffering from Brown Ring Disease (BRD) on Tunisian Coasts

Abstract A total of 13 pathogenic Vibrio spp. bacteria were isolated fro m carpet shell clams (Ruditapes decussatus) with Brown Ring Disease (BRD) in Tunisia. Organisms were identified based on a combination of phenotypic and mo lecular methods (SSP-PCR and 16SrDNA sequencing). Viru lence effects were determined by in vivo testing on R. decussatus and in vitro testing on the Manila clam (Ruditapes philippinarum). All isolates demonstrated biochemical profiles typical of Vibrio spp; nine different biotypes. Three isolates were identified as V.splendidus biovar II TA E2 but the remain ing isolates fell into eight biotypes different fro m each other and fro m the V.tapetis biotype. Species delineation based on 16S rDNA sequencing indicated that the isolated Vibrio spp closely resembled V.chagasii (eight isolates), V.splendidus (two isolates), V.alginolyticus(one isolates), Psychrobacter spp. and Pseudoalteromonas mariniglutinosa (one isolates for each). In vitro cytotoxicity effects and mortalit ies could be induced by the isolates of V.chagasii, V.splendidus and V.alginolyticus at lower dosages than induced by V.tapetis (CECT4600)

Experimental discovery of small RNAs in Staphylococcus aureus reveals a riboregulator of central metabolism

Using an experimental approach, we investigated the RNome of the pathogen Staphylococcus aureus to identify 30 small RNAs (sRNAs) including 14 that are newly confirmed. Among the latter, 10 are encoded in intergenic regions, three are generated by premature transcription termination associated with riboswitch activities, and one is expressed from the complementary strand of a transposase gene. The expression of four sRNAs increases during the transition from exponential to stationary phase. We focused our study on RsaE, an sRNA that is highly conserved in the bacillales order and is deleterious when over-expressed. We show that RsaE interacts in vitro with the 5′ region of opp3A mRNA, encoding an ABC transporter component, to prevent formation of the ribosomal initiation complex. A previous report showed that RsaE targets opp3B which is co-transcribed with opp3A. Thus, our results identify an unusual case of riboregulation where the same sRNA controls an operon mRNA by targeting two of its cistrons. A combination of biocomputational and transcriptional analyses revealed a remarkably coordinated RsaE-dependent downregulation of numerous metabolic enzymes involved in the citrate cycle and the folate-dependent one-carbon metabolism. As we observed that RsaE accumulates transiently in late exponential growth, we propose that RsaE functions to ensure a coordinate downregulation of the central metabolism when carbon sources become scarce

Evidence for the Role of Horizontal Transfer in Generating pVT1, a Large Mosaic Conjugative Plasmid from the Clam Pathogen, Vibrio tapetis

The marine bacterium Vibrio tapetis is the causative agent of the brown ring disease, which affects the clam Ruditapes philippinarum and causes heavy economic losses in North of Europe and in Eastern Asia. Further characterization of V. tapetis isolates showed that all the investigated strains harbored at least one large plasmid. We determined the sequence of the 82,266 bp plasmid pVT1 from the CECT4600T reference strain and analyzed its genetic content. pVT1 is a mosaic plasmid closely related to several conjugative plasmids isolated from Vibrio vulnificus strains and was shown to be itself conjugative in Vibrios. In addition, it contains DNA regions that have similarity with several other plasmids from marine bacteria (Vibrio sp., Shewanella sp., Listonella anguillarum and Photobacterium profundum). pVT1 contains a number of mobile elements, including twelve Insertion Sequences or inactivated IS genes and an RS1 phage element related to the CTXphi phage of V. cholerae. The genetic organization of pVT1 underscores an important role of horizontal gene transfer through conjugative plasmid shuffling and transposition events in the acquisition of new genetic resources and in generating the pVT1 modular organization. In addition, pVT1 presents a copy number of 9, relatively high for a conjugative plasmid, and appears to belong to a new type of replicon, which may be specific to Vibrionaceae and Shewanelleacae

Global Analysis of Extracytoplasmic Stress Signaling in Escherichia coli

The Bae, Cpx, Psp, Rcs, and σE pathways constitute the Escherichia coli signaling systems that detect and respond to alterations of the bacterial envelope. Contributions of these systems to stress response have previously been examined individually; however, the possible interconnections between these pathways are unknown. Here we investigate the dynamics between the five stress response pathways by determining the specificities of each system with respect to signal-inducing conditions, and monitoring global transcriptional changes in response to transient overexpression of each of the effectors. Our studies show that different extracytoplasmic stress conditions elicit a combined response of these pathways. Involvement of the five pathways in the various tested stress conditions is explained by our unexpected finding that transcriptional responses induced by the individual systems show little overlap. The extracytoplasmic stress signaling pathways in E. coli thus regulate mainly complementary functions whose discrete contributions are integrated to mount the full adaptive response

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

« Les nouveaux modes de pilotage de la recherche : quels effets ? » : le séminaire 2014-2015 du Centre d’Alembert de l’Université Paris-Sud

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Transgène et la thérapie génique

À travers l’histoire de l’implication de l’entreprise de biotechnologie Transgène dans des tentatives de développement de produits de thérapie génique, cet article analyse les mécanismes socio-économiques qui ont permis à Transgène, sur la base d’un discours de la promesse, de mobiliser pendant des années des investissements massifs sans aboutir à un seul produit sur le marché après plus de 25 ans. Ce cas est emblématique d’une économie de la promesse caractérisée par une déconnexion durable entre des investissements considérables et l’existence d’un produit ou d’un service commercialisable. La promesse technique ne fonctionne comme moteur d’une telle économie que dans un contexte de politiques publiques, qui, au nom de la priorité à l’innovation comme solution à tous les problèmes socio-économiques, ont permis la mise en place de mécanismes spéculatifs de valorisation financière des promesses.By retracing the history of the attempt of the French biotech company Transgene to develop gene therapy products, this article aims at deciphering the mechanisms that allowed Transgene, on the basis of a discourse of promises, to sustain an enormous capital burn-rate for more than 25 years, without any marketable product yet. This case thus illustrates what can be deemed an economy of promises, characterized by a long-term disconnection between investments and products, but where short-term profit making can still be made or hoped for through the highly speculative financial instruments which were developed in a context of public policies which view technical innovations as solutions to all socio-economical problems

Rôle des petits ARN régulateurs dans le réseau de régulation contrôlant la virulence chez Vibrio splendidus

Vibrio splendidus est une bacterie Gram négative du genre Vibrio. Les Vibrios sont des bactéries motiles, en forme de virgule, vivant essentiellement dans les ecosystèmes marins. Depuis une quinzaine d'années, Vibrio splendidus a été associé a des épisodes estivaux de mortalité de naissains d'huitres en France, jusqu'à compromettre l'économie ostréicole. Cependant on sait encore peu de choses sur l évolution de cette espèce, sa capacité d'adaptation, et ses mécanismes de virulence. De nombreux travaux au cours de ces dernières années ont souligné l'importance des petits ARN non codants (sRNA) dans la régulation des gènes bactériens, en particulier en réponse à l'environnement ainsi qu'au cours de la pathogenèse. Nous avons réalisé une étude de transcriptomique par séquençage à haut débit afin d'établir un répertoire des sRNA chez V. splendidus. Cette analyse transcriptomique nous a permis d'identifier des centaines de sRNAs putatifs, dont la majorité sont spécifiques de cette espèce, une minorité résultant de transferts horizontaux avec d'autres bactéries marines, comme les Shewanellaceae. Les données transcriptomiques ont montré la présence chez V. splendidus de 4 copies du petit ARN CsrB, contrairement aux autres Vibrios qui en ont trois ou deux. Nous avons pu montrer que ces CsrBs jouent un role important dans la physiologie cellulaire en contrôlant la production et/ou la sécrétion de deux proteases jouant un role dans la virulence. De plus, nous avons montré que le réseau de régulation impliquant ces CsrBs est significativement différent des autres Vibrios, indiquant que la présence d'une copie supplémentaire a sans doute entraine un remodelage de ce réseau de régulation.Vibrio splendidus is a Gram negative bacterium of the genus Vibrio. The Vibrios are motile, comma-shaped bacteria, living mainly in marine ecosystems. Over the past fifteenyears, Vibrio splendidus has been associated with oyster summer mortality episodes inFrance, generating heavy economic losses. However, still little is known about the evolutionof this species, its adaptive capacity, and the mechanisms of virulence. Many works in recentyears have stressed the importance of small noncoding RNAs (sRNAs) in bacterial generegulation, particularly in response to the environment as well as during pathogenesis. Wedid a transcriptomic study by high-throughput sequencing in order to explore the sRNArepertoire in V. splendidus. This transcriptomic analysis allowed us to identify hundreds ofputative sRNAs, the majority of which being specific of this species, a minority resulting fromhorizontal transfers with other marine bacteria, such as the Shewanellaceae. Transcriptomicdata showed the presence of 4 copies of the small RNA CsrB in V. splendidus, unlike otherVibrios which have two or three. We have shown that these CsrBs play an important role incell physiology by controlling the production and/or secretion of two proteases playing a rolein virulence. In addition, we have shown that the regulatory network involving these CsrBs issignificantly different from other Vibrios, indicating that the presence of an extra copy hasindeed resulted in a reshaping of the regulatory network.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Science et démocratie : une articulation difficile mais nécessaire

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