Cyanobacterial blooms are known to modify the aquatic ecosystem functioning by strongly decreasing the biodiversity of the phytoplankton communities, and enhancing the biomass production. Moreover, they could generate health problems, by their capacities of producing harmful cyanotoxines for humans and animals. Although it is now well established that nutrient loadings (mostly N and P) and climate conditions (water column stability) play a major role in the determinism of the phytoplankton blooms; numerous factors and processes involved in the enhancement of these proliferations, are still poorly understood. For example, positive/negative interactions within the microbial communities could play a major role. Few knowledge of the phycosphere (equivalent to the rhizosphere concept) of the cyanobacteria is available, although the matter and energy fluxes (mucus and exudates, N2 fixation products, organic matter mineralization) are certainly intense within the phycosphere and the cyanobacteria. In the project proposed herein, the bacterial communities will be studied within the phycosphere of two toxic cyanobacteria, Microcystis aeruginosa, and Aphanizomenon flos aquae, well known for their proliferations in many worldwide ecosystems. During the seasonal bloom (May to October), the succession of both species within the phytoplankton community was observed: with a predominance of A. flos aquae in May-June, followed by the codominance in June-July, and the dominance of M. aeruginosa from July to October. More precisely, in this project we will determine the bacterial structural and functional diversities and activities within the phycospheres, with a special attention given to the ones involved in the N recycling. Effectively, M. aeruginosa is not able to fix N2, while A. flos aquae can develop differentiated cells for the N2 fixation (heterocysts) within their filaments. Thus our main hypothesis is that the N2-fixing capability will have strong impact on the diversity and functioning of the bacterial consortia associated to both cyanobacterial types. To test this, we will develop an integrative approach based on metatranscriptome analyses, molecular quantification of genes involved in the N recycling, combined with the 15N pool dilution method and measures of potential activities. These approaches would allow to: (i) compare the structure and composition of the bacterial communities associated to both cyanobacteria, and the free-living bacteria fraction (ii) to characterize the metabolism and activities of the genes involved in the N recycling within the active bacterial fraction, (iii) determine the N fluxes and N20 emissions within the bacteria-cyanobacteria consortia, in comparison to the ones from the free-living bacterial fraction. Altogether, these results will inform us on the relationships existing between the cyanobacteria and the bacteria associated, which could play a significant role in the ecological success of the cyanobacteria in aquatic ecosystems.

VIRAGE in French means turn/change of direction. Galaxies are evolving systems that experience transformations during their lifetime: their orbits, mass accretion and star formation histories and finally morphology all change. This happens in the context of a living Universe in which structures assemble by the gravitational growth of initial dark matter fluctuations to create the massive galaxy clusters we observe today. How much galaxy transformations are driven by the physics of this gravitational assembly and how much by the physics of baryons is one of the most hotly debated questions today. The underlying key question is whether the dominant processes are internal to galaxies (nature) or due to their interactions with the environment (nurture). We address this question by a detailed characterization of environmental effects within the densest environment of the nearby Universe, the Virgo galaxy cluster. We aim to examine in greater detail than ever before the galaxies in this system, their interactions and the interaction with their surrounding medium in the core of the cluster as well as its peripheral regions. Our goal is to provide a reference analysis of galaxies in these different cluster environments that is statistically complete in range of galaxy mass and multi-wavelength coverage. This is only possible because of its proximity, which makes of Virgo the only galaxy cluster in which baryonic structures can be studied in such great detail, from the brightest to the very faintest galaxies, and including the extremely faint tidal structures around them. Over the next few years, a wealth of surveys of this cluster will revolutionize the way we study it, because of their unprecedented depth, spatial and wavelength coverage. They will discover new objects and expand our insight on the star formation and interacting history of galaxies in this remarkable system. The strength of our team lies in our involvement in all of these major surveys, as either PIs or Co-Is . Our collaboration will therefore have the access, resources and expertise to fully capitalize on this outstanding data set. Our analysis will primarily draw on three surveys: the Next Generation Virgo Survey, the NGVS-IR, and GUViCS, combined with complementary data when needed for our scientific goals. We propose to combine the unique data from these three surveys to characterize the effects of environment on galaxy star formation histories, spatial distribution, and on the intragalactic medium. Our analysis will: -discover new faint galaxies and low surface brightness features (tidal tails, stellar streams) -produce a distance catalog of Virgo galaxies and examine environmental signatures as a function of local (instead of projected) galaxy density -enable spectro-chemical modeling of environmental effects on galaxy spectral energy distributions, and the reconstruction of galaxy star formation histories from the brightest to the faintest objects When completed, our results will be used for decades as benchmarks in the characterization of galaxies changing in a dense environment, from the most massive to the very faintest, and a reference for future comparison of galaxies in the field.

It has become evident that a large number of proteins fulfill essential biological functions, while lacking a well-defined three-dimensional structure. This is in direct contrast to Pauling’s rule, which states that a biologically active protein requires a native three-dimensional structure. Intrinsically disordered proteins (IDPs) constitute an important part of the eukaryotic proteome. The description of their conformational space is an active field of biophysical research. However, in striking contrast to folded proteins, description of their dynamics is nearly completely missing. Nevertheless, it is highly likely that dynamical behavior also play crucial roles in the biological functions of IDPs. Here, we introduce a variety of novel and powerful NMR relaxation-based approaches to sample the dynamics of IDPs. Two different, yet complementary, NMR methodologies will be implemented. First, we will develop original and use existing NMR experiments to gather a complete set of information on the motions of the protein backbone of IDPs. This unprecedented set of experimental data on the dynamics of many internuclear backbone vectors and the correlation of these motions will be essential to understand the dynamics of unstructured proteins on a broad range of timescales. Second, we will develop new, innovative hardware for field-cycling studies of relaxation, which offers the combined advantages of high-resolution NMR spectroscopy and relaxometry. This information will be collected on systems with important biological functions and that constitute potential therapeutical targets (Parkinson's disease, cancer). These proteins are: (i) two disordered natural partners of protein phosphatase 1, differing by their degree of residual structure, namely I-2 (high levels of residual structures), and spinophilin (low levels); (ii) Engrailed 2, a transcription factor that possesses a well-folded homeodomain and a long, mostly unstructured N-terminal domain. Thus, the investigation of these systems will cover a broad range of typical behaviors of IDPs that are currently described in the literature and thus provide much needed information. The newly gained insight of the dynamics at multiple timescales, as well as the detailed understanding of the nature of these motions will be essential to understand the mechanisms and function of IDPs.