Connectivité spatiale et diversité des espèces: Mise en place d’un réseau de conservation dans le Parc National du Mercantour

La thématique des forêts anciennes et des forêts matures a été au cœur du séminaire physique du GT Forêt-Eau, avec l'organisation le 27 octobre 2015 d'une journée d'échanges et de visite, associant une douzaine de partenaires (INRA, IRSTEA, Purpan, RNF, FPNR, CBNMC...). Au delà, PNF [Parcs Nationaux de France] continuera à suivre les différents projets en cours, menés par des Parcs nationaux ou d'autres partenaires, et à envisager d'autres projets collectifs pour aller plus loin dans la connaissance des forêts anciennes et matures

Biofilm monitoring as a tool to assess the efficiency of artificial reefs as substrates: Toward 3D printed reefs

International audienceHabitat destruction is one of the main causes of the decline of biodiversity and of fishery resources in the marine environment. An artificial reef (AR) could be a tool for protecting or restoring these habitats and their declining biodiversity, and also help to enhance sustainable fisheries. The goal is to design non-polluting structures that best mimic the complexity of natural habitats in order to improve their service to the community. To date, the assessment of reef performance has been mostly focused on fish assemblages and species of ecological and/or socio-economic interest, and has disregarded the biofilm communities that determine the first level of an AR’s trophic network. In this work, we used biofilm formation to compare the quality of substrates used as building parts for an AR, in order to optimize an eco-friendly material that will be used to design a new generation of ARs produced by giant 3D printers. The structure of the photosynthetic communities has been identified using pigment biomarkers and their production of exudates has been analysed. These polymeric substances were quantified in terms of total sugar and protein concentrations. They were further analysed in terms of amino acid content. We found no significant differences between the micro-algae communities developed on the different substrates. These photosynthetic communities were mainly composed of diatoms, prasinophytes, haptophytes, and dinoflagellates. However, we showed that the material for ARs is crucial for biofilm development, especially with regard to its secretions of sugar. The choice of an appropriate substrate for AR construction is thus of particular importance since biofilm secretions determine the organic substrate on which sessile macro-organisms will settle

Composition comprising a lasso peptide formulated in a pharmaceuticallyacceptable nanoemulsion

The present invention relates to a composition comprising a lasso peptide formulated in a pharmaceutically acceptable nanoemulsion and an antibiotic, to said composition for use as a medicine, and to a method for producing said composition. The composition of the present invention finds an application for example for thetreatment of an infection by a Gram-positive bacterium

Interaction of the 14-residue peptaibols, harzianins HC, with lipid bilayers: permeability modifications and conductance properties

AbstractHarzianins HC are a series of 14-residue peptaibols containing three Aib-Pro motives separated by sequences of two usual amino acids (Aib-Pro-Xaa-Xaa)n. They are organized in a subtype of the 310-helix, which results in an approximate length of about 27–30 Å for the helical rods, allowing them to span a bilayer. Permeabilization of small unilamellar vesicles composed of zwitterionic lipids (egg phosphatidylcholine/cholesterol 7/3 and 8/2) by harzianins HC was observed, as well as voltage-gated macroscopic conductance and single-channel formation in planar lipid bilayers (DOPE/POPC 7/3). The permeabilization process was shown to increase with increasing the helix global hydrophobicity. The ion channel-forming properties appeared rather favoured by an increase in the peptide amphipathicity. The set of conductance levels increasing in geometrical progression, reflecting the sequential uptake and release of monomers which is characteristic of the barrel-stave model for ion-channels described for alamethicin was not observed. The passage of ions through the bilayer would rather be the result of a set of aggregates with fixed numbers of monomers formed in the bilayer. The permeability process and the voltage-gated properties could thus result from different mechanisms showing that harzianins HC can permeabilize membranes via bilayer destabilization or channels, depending on the membrane system, composition and application of voltage

Spatial patterns of tree-related microhabitats: key factors and ecological significance for the conservation of the associated biodiversity

Tree-related microhabitats (TreMs) are specific, well delineated above-ground tree morphological singularities occurring on living or standing dead trees. TreMs are key features for many taxa and contribute in the complex network of forest resources for biodiversity (1). Large and broadleaved trees bear most of the TreMs within a forest stand (2). The spatial pattern of TreMs is however not only influenced by the spatial distribution of these noteworthy trees, but also by a wide range of natural stochastic, abiotic and biotic processes as well as forestry operations (3). A better knowledge of spatial patterns of TreMs in contrasted forest conditions would help us to promote more biodiversity-friendly forest management practices. First we explored spatial patterns of two TreM types, pivotal for saproxylic beetles, i.e. cavities and polypores, in temperate old-growth forests and compared them with patterns in stands in managed forests, analyzing a compiled European database focusing on beech and oak trees. Secondly, we analyzed the response of TreM-associated saproxylic beetle assemblages, sampled by emergence traps set up on targeted TreMs, to variations in spatial patterns of cavities and polypores. For instance, based on several case studies, we addressed the following questions: is the dissimilarity of assemblages hosted by cavities related to the between-cavity geometric distance? How is the occupancy probability of a cavity-dwelling beetle affected by the distance to the closest occupied cavity? Does an increasing sporocarp density at local scales foster the species richness of fungus-dwelling beetles at the sporocarp scale? Finally, we discuss deemed consequences for conservation of TreM-associated taxa in managed forests. 1-Larrieu L., Paillet Y., Bütler R., Kraus D., Krumm F., Lachat T., Michel A. K., Regnery B., Vandekerkhove K., Winter S. (2018). Tree related microhabitats in temperate and Mediterranean forests of Europe: a reference list and inventory baseline for forest biodiversity research and monitoring. Ecological Indicator 84: 194-207 2-Larrieu L., Cabanettes A. (2012). Species, live status, and diameter are important tree features for diversity and abundance of tree-microhabitats in subnatural montane beech-fir forests. Canadian Journal of Forest Research 42: 1433-1445. 3-Larrieu L., Cabanettes A., Brin A., Bouget C., Deconchat M. (2014). Tree microhabitats at the stand scale in montane beech-fir forests: practical information for taxa conservation in forestry. European journal of Forest Research, 133:355-367peerReviewe

Microcin C51 Plasmid Genes: Possible Source of Horizontal Gene Transfer

Microcin C51 (MccC51) is an antimicrobial nucleotide-heptapeptide produced by a natural Escherichia coli strain. A 5.7-kb fragment of the pC51 plasmid carrying the genes involved in MccC51 production, secretion, and self-immunity was sequenced, and the genes were characterized. The sequence of the MccC51 gene cluster is highly similar to that of the MccC7 gene. Recombinant plasmids carrying different combinations of the mcc genes involved in the MccC51 production or immunity were constructed to characterize their functional roles. The mccA, mccB, mccD, and mccE genes are involved in MccC51 production, while the mccC and mccE genes are responsible for immunity to MccC51. The mcc gene cluster is flanked by 44-bp direct repeats. Amino acid sequence comparisons allowed us to propose functions for each Mcc polypeptide in MccC51 biosynthesis. Plasmid pUHN containing the cloned mccA, mccB, mccC, and mccE genes, but lacking mccD, directed the synthesis of MccC51p, a substance chemically related to MccC51. MccC51p exhibited weak antibiotic activity against E. coli and was toxic to the producing cells. The immunity to exogenous MccC51 determined by the mccC and mccE genes did not overcome the toxic action of MccC51p on the producing cells. The G+C content of the MccC51 operon, markedly lower than that of the E. coli genome, and the presence of direct repeats suggest the possibility of horizontal transfer of this gene cluster

Solution structure of microcin J25, the single macrocyclic antimicrobial peptide from Escherichia coli.

International audienceThe three-dimensional solution structure of microcin J25, the single cyclic representative of the microcin antimicrobial peptide class produced by enteric bacteria, was determined using two-dimensional 1H NMR spectroscopy and molecular modeling. This hydrophobic 21-residue peptide exhibits potent activity directed to Gram-negative bacteria. Its primary structure, cyclo(-V1GIGTPISFY10GGGAGHVPEY20F-), has been determined previously [Blond, A., Péduzzi, J., Goulard, C., Chiuchiolo, M. J., Barthélémy, M., Prigent, Y., Salomón, R.A., Farías, R.N., Moreno, F. & Rebuffat, S. (1999) Eur. J. Biochem., 259, 747-755]. Conformational parameters (3JNHCαH coupling constants, quantitative nuclear Overhauser enhancement data, chemical shift deviations, temperature coefficients of amide protons, NH-ND exchange rates) were obtained in methanol solution. Structural restraints consisting of 190 interproton distances inferred from NOE data, 11 φ backbone dihedral angle and 9 χ1 angle restraints derived from the coupling constants and three hydrogen bonds in agreement with the amide exchange rates were used as input for simulated annealing calculations and energy minimization in the program xplor. Microcin J25 adopts a well-defined compact structure consisting of a distorted antiparallel β sheet, which is twisted and folded back on itself, thus resulting in three loops. Residues 7-10 and 17-20 form the more regular part of the β sheet. The region encompassing residues Gly11-His16 consists of a distorted β hairpin, which divides into two small loops and is stabilized by an inverse γ turn and a type I′β turn. The reversal of the chain leading to the Phe21-Pro6 loop results from a mixed β/γ turn. A cavity, in which the hydrophilic Ser8 side-chain is confined, is delimited by two crab pincer-like regions that comprise residues 6-8 and 18-1