X-rays constraints on sub-GeV Dark Matter

We present updated constraints on 'light' Dark Matter (DM) particles with masses between 1 MeV and 5 GeV. In this range, we can expect DM-produced $e^\pm$ pairs to up-scatter low-energy ambient photons in the Milky Way via the Inverse Compton process, and produce a flux of X-rays that can be probed by a range of space observatories. Using diffuse X-ray data from XMM-Newton, INTEGRAL, NuSTAR and Suzaku, we compute the strongest constraints to date on annihilating DM for 200 MeV $< m_{\rm DM} <$ 5 GeV and decaying DM for 100 MeV $< m_{\rm DM} <$ 5 GeV.Comment: Contribution to the 34th Rencontres de Blois on Particle Physics and Cosmology (Blois 2023), the XVIII International Conference on Topics in Astroparticle and Underground Physics (TAUP 2023) and TeV Particle Astrophysics (TeVPA) 202

Feasibility experiments on time-resolved fluorosensing applied to oil slicks

The introduction of time resolved observations can provide a very penetrating tool in the practice of laser fluorosensing. The investigations have demonstrated a relevance of multispectral, time resolved analysis for oil fingerprinting. By comparative studies on a variety of crude oils and their most significant fractions, it was found that the process of time decay in a composite oil is characterized by a few steps, which are associated with specific components in the medium light range. The average decay times of these pure fractions are markedly differentiated as to absolute values and spectral spread; as a consequence, the corresponding parameters in the resultant crude are quite sensitive to the particular mixture of these components. Measurements of the time response give then a finer discrimination between oil classes, depending on the relative content of certain fractions. Experiments were pursued with an improved fluorosensor facility, in order to test the application of time resolved fluorosensing to remote samples on water

Putting all the X in one basket: Updated X-ray constraints on sub-GeV Dark Matter

Sub-GeV dark matter particles can annihilate or decay producing e^\pm pairs which upscatter the low-energy photon fields in the Galaxy and generate an X-ray emission (via the Inverse Compton effect). Using X-ray data from Xmm-Newton, Integral, NuStar and Suzaku, we derive new constraints on this class of dark matter (DM). In the annihilation case, our new bounds are the strongest available for DM masses above 180 MeV, reaching < 10^-28 cm^3/s for m_DM ~ 1 GeV. In the decay case, our bounds are the strongest to date over a large fraction of the considered mass range, constraining tau > 10^28 s for m_DM ~ 1 GeV and improving by up to 3 orders of magnitude upon existing limits.Comment: 16 pages, 9 figure

Temporal transcriptomic response during arsenic stress in Herminiimonas arsenicoxydans

Background: Arsenic is present in numerous ecosystems and microorganisms have developed various mechanisms to live in such hostile environments. Herminiimonas arsenicoxydans, a bacterium isolated from arsenic contaminated sludge, has acquired remarkable capabilities to cope with arsenic. In particular our previous studies have suggested the existence of a temporal induction of arsenite oxidase, a key enzyme in arsenic metabolism, in the presence of As(III). Results: Microarrays were designed to compare gene transcription profiles under a temporal As(III) exposure. Transcriptome kinetic analysis demonstrated the existence of two phases in arsenic response. The expression of approximatively 14% of the whole genome was significantly affected by an As(III) early stress and 4% by an As(III) late exposure. The early response was characterized by arsenic resistance, oxidative stress, chaperone synthesis and sulfur metabolism. The late response was characterized by arsenic metabolism and associated mechanisms such as phosphate transport and motility. The major metabolic changes were confirmed by chemical, transcriptional, physiological and biochemical experiments. These early and late responses were defined as general stress response and specific response to As(III), respectively. Conclusion: Gene expression patterns suggest that the exposure to As(III) induces an acute response to rapidly minimize the immediate effects of As(III). Upon a longer arsenic exposure, a broad metabolic response was induced. These data allowed to propose for the first time a kinetic model of the As(III) response in bacteria

Organization of the TC and TE cellular T-DNA regions in Nicotiana otophora and functional analysis of three diverged TE-6b genes.

Nicotiana otophora contains Agrobacterium-derived T-DNA sequences introduced by horizontal gene transfer (Chen et al., 2014). Sixty-nine contigs were assembled into four different cellular T-DNAs (cT-DNAs) totalling 83 kb. TC and TE result from two successive transformation events, each followed by duplication, yielding two TC and two TE inserts. TC is also found in other Nicotiana species, whereas TE is unique to N. otophora. Both cT-DNA regions are partially duplicated inverted repeats. Analysis of the cT-DNA divergence patterns allowed reconstruction of the evolution of the TC and TE regions. TC and TE carry 10 intact open reading frames. Three of these are TE-6b genes, derived from a single 6b gene carried by the Agrobacterium strain which inserted TE in the N. otophora ancestor. 6b genes have so far only been found in Agrobacterium tumefaciens or Agrobacterium vitis T-DNAs and strongly modify plant growth (Chen and Otten, 2016). The TE-6b genes were expressed in Nicotiana tabacum under the constitutive 2 × 35S promoter. TE-1-6b-R and TE-2-6b led to shorter plants, dark-green leaves, a strong increase in leaf vein development and modified petiole wings. TE-1-6b-L expression led to a similar phenotype, but in addition leaves show outgrowths at the margins, flowers were modified and plants became viviparous, i.e. embryos germinated in the capsules at an early stage of their development. Embryos could be rescued by culture in vitro. The TE-6b phenotypes are very different from the earlier described 6b phenotypes and could provide new insight into the mode of action of the 6b genes.journal articleresearch support, non-u.s. gov't2018 042018 03 23importe

Subinhibitory Arsenite Concentrations Lead to Population Dispersal in Thiomonas sp.

Biofilms represent the most common microbial lifestyle, allowing the survival of microbial populations exposed to harsh environmental conditions. Here, we show that the biofilm development of a bacterial species belonging to the Thiomonas genus, frequently found in arsenic polluted sites and playing a key role in arsenic natural remediation, is markedly modified when exposed to subinhibitory doses of this toxic element. Indeed, arsenite [As(III)] exposure led to a considerable impact on biofilm maturation by strongly increasing the extracellular matrix synthesis and by promoting significant cell death and lysis within microcolonies. These events were followed by the development of complex 3D-biofilm structures and subsequently by the dispersal of remobilized cells observed inside the previously formed hollow voids. Our results demonstrate that this biofilm community responds to arsenite stress in a multimodal way, enhancing both survival and dispersal. Addressing this complex bacterial response to As(III) stress, which might be used by other microorganisms under various adverse conditions, may be essential to understand how Thiomonas strains persist in extreme environments

A new family of periplasmic-binding proteins that sense arsenic oxyanions

Arsenic contamination of drinking water affects more than 140 million people worldwide. While toxic to humans, inorganic forms of arsenic (arsenite and arsenate), can be used as energy sources for microbial respiration. AioX and its orthologues (ArxX and ArrX) represent the first members of a new sub-family of periplasmic-binding proteins that serve as the first component of a signal transduction system, that's role is to positively regulate expression of arsenic metabolism enzymes. As determined by X-ray crystallography for AioX, arsenite binding only requires subtle conformational changes in protein structure, providing insights into protein-ligand interactions. The binding pocket of all orthologues is conserved but this alone is not sufficient for oxyanion selectivity, with proteins selectively binding either arsenite or arsenate. Phylogenetic evidence, clearly demonstrates that the regulatory proteins evolved together early in prokaryotic evolution and had a separate origin from the metabolic enzymes whose expression they regulate

A Tale of Two Oxidation States: Bacterial Colonization of Arsenic-Rich Environments

Microbial biotransformations have a major impact on contamination by toxic elements, which threatens public health in developing and industrial countries. Finding a means of preserving natural environments—including ground and surface waters—from arsenic constitutes a major challenge facing modern society. Although this metalloid is ubiquitous on Earth, thus far no bacterium thriving in arsenic-contaminated environments has been fully characterized. In-depth exploration of the genome of the β-proteobacterium Herminiimonas arsenicoxydans with regard to physiology, genetics, and proteomics, revealed that it possesses heretofore unsuspected mechanisms for coping with arsenic. Aside from multiple biochemical processes such as arsenic oxidation, reduction, and efflux, H. arsenicoxydans also exhibits positive chemotaxis and motility towards arsenic and metalloid scavenging by exopolysaccharides. These observations demonstrate the existence of a novel strategy to efficiently colonize arsenic-rich environments, which extends beyond oxidoreduction reactions. Such a microbial mechanism of detoxification, which is possibly exploitable for bioremediation applications of contaminated sites, may have played a crucial role in the occupation of ancient ecological niches on earth