RcnB Is a Periplasmic Protein Essential for Maintaining Intracellular Ni and Co Concentrations in Escherichia coli

International audienceNickel and cobalt are both essential trace elements that are toxic when present in excess. The main resistance mechanism that bacteria use to overcome this toxicity is the efflux of these cations out of the cytoplasm. RND (resistance-nodulation-cell division)- and MFS (major facilitator superfamily)-type efflux systems are known to export either nickel or cobalt. The RcnA efflux pump, which belongs to a unique family, is responsible for the detoxification of Ni and Co in Escherichia coli. In this work, the role of the gene yohN, which is located downstream of rcnA, is investigated. yohN is cotranscribed with rcnA, and its expression is induced by Ni and Co. Surprisingly, in contrast to the effect of deleting rcnA, deletion of yohN conferred enhanced resistance to Ni and Co in E. coli, accompanied by decreased metal accumulation. We show that YohN is localized to the periplasm and does not bind Ni or Co ions directly. Physiological and genetic experiments demonstrate that YohN is not involved in Ni import. YohN is conserved among proteobacteria and belongs to a new family of proteins; consequently, yohN has been renamed rcnB. We show that the enhanced resistance of rcnB mutants to Ni and Co and their decreased Ni and Co intracellular accumulation are linked to the greater efflux of these ions in the absence of rcnB. Taken together, these results suggest that RcnB is required to maintain metal ion homeostasis, in conjunction with the efflux pump RcnA, presumably by modulating RcnA-mediated export of Ni and Co to avoid excess efflux of Ni and Co ions via an unknown novel mechanism

Structure, electrochemical properties and functionalization of amorphous CN films deposited by femtosecond pulsed laser ablation

Amorphous carbon nitride (a-C:N) material has attracted much attention in research and development. Recently, it has become a more promising electrode material than conventional carbon based electrodes in electrochemical and biosensor applications. Nitrogen containing amorphous carbon (a-C:N) thin films have been synthesized by femtosecond pulsed laser deposition (fs-PLD) coupled with plasma assistance through Direct Current (DC) bias power supply. During the deposition process, various nitrogen pressures (0 to 10 Pa) and DC bias (0 to ¿ 350 V) were used in order to explore a wide range of nitrogen content into the films. The structure and chemical composition of the films have been studied by using Raman spectroscopy, electron energy-loss spectroscopy (EELS) and high-resolution transmission electron microscopy (HRTEM). Increasing the nitrogen pressure or adding a DC bias induced an increase of the N content, up to 21 at.%. Nitrogen content increase induces a higher sp2 character of the film. However DC bias has been found to increase the film structural disorder, which was detrimental to the electrochemical properties. Indeed the electrochemical measurements, investigated by cyclic voltammetry (CV), demonstrated that a-C:N film with moderate nitrogen content (10 at.%) exhibited the best behavior, in terms of reversibility and electron transfer kinetics. Electrochemical grafting from diazonium salts was successfully achieved on this film, with a surface coverage of covalently bonded molecules close to the dense packed monolayer of ferrocene molecules. Such a film may be a promising electrode material in electrochemical detection of electroactive pollutants on bare film, and of biopathogen molecules after surface grafting of the specific affinity receptor.This work is produced with the financial support of the Future Program Lyon Saint-Etienne (PALSE) from the University of Lyon (ANR-11-IDEX-0007), under the “Investissements d'Avenir” program managed by the National Agency Research (ANR)

Blood Bacterial Profiles Associated With Human Immunodeficiency Virus Infection and Immune Recovery

[EN] Human immunodeficiency virus (HIV) infection impairs mucosal immunity and leads to bacterial translocation, fueling chronic inflammation and disease progression. While this is well established, questions remain about the compositional profile of the translocated bacteria, and to what extent it is influenced by antiretroviral therapy (ART). Using 16S ribosomal DNA targeted sequencing and shotgun proteomics, we showed that HIV increases bacterial translocation from the gut to the blood. HIV increased alpha diversity in the blood, which was dominated by aerobic bacteria belonging to Micrococcaceae (Actinobacteria) and Pseudomonadaceae (Proteobacteria) families, and the number of circulating bacterial proteins was also increased. Forty-eight weeks of ART attenuated this phenomenon. We found that enrichment with Lactobacillales order, and depletion of Actinobacteria class and Moraxellaceae and Corynebacteriacae families, were significantly associated with greater immune recovery and correlated with several inflammatory markers. Our findings suggest that the molecular cross talk between the host and the translocated bacterial products could influence ART-mediated immune recovery.This work was supported by the Instituto de Salud Carlos III (Plan Estatal de I+D+i 2013–2016, projects PI15/00345 and PI18/00154); the Fundación Asociación Española Contra el Cáncer within the European Research Era-NET aligning national/regional translational cancer research programs and activities program (grant AC17/00019) and cofinanced by the European Development Regional Fund; and Plan Estatal de I+D+i 2013–2016 (grant PT17/0019 to the Proteomics Facility of the Spanish National Center for BIotechnology)

MIP-based impedimetric sensors

International audienceMolecular imprinting technique allows the preparation of tailor-made materials with high recognition faculty towards target molecules. Molecular imprinted polymers (MIPs) are more robust, easier to manipulate and cheaper than biological receptors, constituting very attractive alternatives to biomolecules as recognition elements in the elaboration of biosensors. In this paper, the principles and advantages of MIP-based impedimetric sensors are described and some examples of application in the biological or environmental fields are given

Conception et caractérisation de nouvelles biointerfaces nanostructurées pour l’élaboration de biocapteurs électrochimiques ultrasensibles (Keynote conference)

International audienc

Quand la littérature rencontre le théâtre

La rencontre du théâtre et de la littérature est compliquée, car elle se heurte à la frontière qui existe entre le livre et la scène. Chaque fois, le théâtre doit d'une nouvelle manière convaincre l'écrivain de sa nécessité puisqu' il pourrait s'arrêter à la nécessité première du livre. Il s'agit toujours d'un territoire à réinventer

Leçon

Florence March. Pour commencer, je voudrais paradoxalement partir de la fin, c’est-à-dire du dernier spectacle, Un mage en été, parce qu’il cristallise d’une certaine manière la rencontre de la littérature et du théâtre. La dernière phrase du texte de Cadiot, « Vous n’imaginez pas ce que peut un corps », s’entend à la fois comme un hommage et une ouverture de la littérature aux arts de la scène. Le mage lui-même apparaît comme la métaphore de l’artiste, qu’il soit écrivain, metteur en scène o..