Efficacité de biofilms de bactéries As-oxydantes pour l'étape de traitement biologique d'eaux potabilisables arséniées

L'arsenic est un métalloïde toxique dont la présence, relativement fréquente, dans les eaux et les sols est liée soit au fond géochimique, soit aux activités humaines. En ce qui concerne les eaux destinées à la consommation, la législation impose une concentration maximale en arsenic de 10 µg.L-1. Les effets nocifs de l'arsenic sur la santé humaine rendent nécessaire le développement de technologies efficaces et peu couteuse pour éliminer cet élément des eaux potables, ainsi que dans les aquifères pollués et dans les effluents miniers (Wang et Zhao, 2009). Une unité de traitement biologique d'eaux potabilisable faiblement arséniée (As< 50µg/L), couplée à une unité de piégeage de l'As en sortie du bioréacteur, a été mise en œuvre sur un site réel afin d'étudier la robustesse du bioprocédé. Un bioréacteur contenant de la pouzzolane (matériau utilisé dans les traitements d'eaux) a été préalablement ensemencé par une souche bactérienne As(III) oxydante autotrophe (Thiomonas arsenivorans) (Battaglia-Brunet et al., 2002, Michon et al., 2010 ; Wan et al., 2010) puis alimenté par l'eau issue du forage à température ambiante (15-17°C) avec un fonctionnement discontinu (asservissement de l'alimentation du bioréacteur à la pompe du forage d'alimentation en eau). Le suivi du développement du biofilm As(III) oxydant au cours du traitement biologique a été réalisé par la recherche des gènes codant pour l'ARNr 16S (diversité bactérienne totale) et ceux codant pour une arsénite oxydase (aoxB) (diversité des bactéries As(III)-oxydantes). Ce suivi a montré une colonisation rapide et stable du support minéral par des bactéries endogènes de l'eau à traiter. Le rendement d'oxydation de l'étape d'oxydation biologique est compris entre 54 et 100 % avec des temps de séjour de 30 minutes à 7 minutes qui sont comparables à des temps de séjour de techniques classiques de traitement. Les concentrations résiduelles en As en sortie du procédé complet (oxydation biologique + piégeage) sont inférieures à 1 µg/L, et qui sont donc très encourageants pour une application industrielle

Adsorption de l'arsenic présent dans les effluents issus de dépôts de sargasses par des matériaux riches en oxydes de fer

International audienceLes côtes du bassin Caribéen subissent depuis 2011 des échouements saisonniers et massifs d’algues appartenant au genre Sargassum. Les algues collectées et stockées à terre libèrent, au cours de leur dégradation et de leur lessivage par les eaux de pluie, l’arsenic (As) qu’elles avaient accumulé en mer, soit de 50 à 80 mg d’As par kg d’algue sèche. Les effluents ainsi générés peuvent contenir jusqu’à plusieurs mg/L d’As (Devault et al., 2020). L’adsorption sur des matériaux riches en oxydes de fer (Fe) est une des familles de procédés couramment appliqués pour traiter les eaux arséniées. L’objectif de la présente étude était de déterminer si l’adsorption sur des matières minérales naturelles, riches en Fe et abondantes dans les régions affectées par les échouements de Sargasse, pourrait être développée en tant que stratégie de traitement des eaux arséniées issues des sites de stockage

As(III) biological oxidation by CAsO1 consortium in fixed-bed reactors

International audienceIn water treatment, removal of arsenite, the most toxic arsenic inorganic form, consists often in its oxidation, followed by precipitation or adsorption step. In this work, this oxidation step was done by a biological process, using an autotrophic bacterial consortium named CAsO1, isolated from a gold mining site. A pilot plant was built, consisting of two biological fixed beds, inoculated with the CAsO1 consortium and fed with synthetic water spiked with As(III). Firstly, the hydrodynamic parameters were determined. The residence time distribution modelling showed a plug flow distribution with low diffusion phenomena. Secondly, the kinetic analysis, considering a first order reaction, made it possible to calculate the oxidation kinetic constant (0.04 min_1) and showed a heterogeneous distribution of the active biomass along the reactor. Batch experiments conducted with parts of the bed-support made it possible to characterize this kind of distribution. Finally, the hydrodynamic and kinetic studies enabled us to propose a design approach for such a biological treatment process

Removal of arsenic from leachates of decaying Sargassum biomass in a natural iron material-based biofilter

International audienceGroundings of algae belonging to the genus Sargassum have affected the coasts of the Caribbean basin since 2011. The algal biomass, dumped near the littoral releases, during degradation and leaching by rainwater, some arsenic (As) that was accumulated at sea: 50 to 80 mg of As per kg of dry matter. One of the objectives of the SargAs&CLD project funded by the ANR (Sargassum Joint call 2019) was to develop low-cost passive treatment solutions to remove As from these leachates. Adsorption on iron minerals is one of the most efficient processes to immobilize As, often applied in classical water treatment plants. However, this option was never tested with complex effluents, containing high concentration levels of salts and diverse organic compounds, such as in Sargassum leachates. Moreover, industrial adsorbents are expensive. The present study was thus performed with a natural iron-rich (mainly in the form of goethite) soil available in the Martinique Island, in order to develop a biofiltration process based on the use of local raw materials. First, a metric pilot was used to produce natural Sargassum leachates containing As, by simulating, in laboratory conditions, the degradation of algal biomass during storage and exposure to raining events. The early effluents contained 3 to 7 mg/L As, including AsIII, AsV, dimethyl AsV and arsenobetaine. Then, they were used to test a biofiltration process with the aim to retain arsenic. According to the high pH of the effluents (7.5 to 9.5), AsIII was supposed to be more efficiently adsorbed than AsV, thus the biofilter worked in anaerobic conditions favoring AsV bio-reduction. FeIII bio-reduction was also expected in order to induce the formation, at the outlet of the biofilter, of new amorphous FeIII-oxides presenting a higher potential for As adsorption than crystallized FeIII minerals. A laboratory (300 mL) biofilter was continuously fed for 5 months with the Sargassum leachates maintained under anaerobic conditions. The feeding solution was initially supplied without any modification, then enriched with acetate, a well-known electron donor in bacterial anaerobic respiration processes. A diverse bacterial community that evolved with time was retrieved by 16S rRNA gene metabarcoding. Acetate seemed to improve the efficiency of As removal in the biofilter (from 40% to 90% As trapping) that was associated with the production of solid FeII-bearing phases and removal of AsV from the water phase. Results show the potential of natural local soils to develop passive biofilters removing As from Sargassum leachates

Caractérisation d'un biofilm de bactéries As(III) oxydantes lors du traitement biologique d'eaux arseniées en bioréacteurs à lit-fixe

Les effets nocifs de l'arsenic sur la santé humaine rendent nécessaire le développement de technologies efficaces et peu couteuse pour éliminer cet élément des eaux potables, ainsi que dans les aquifères polluées et dans les effluents miniers (Wang et Zhao, 2009). La limite maximale admissible dans les eaux destinées à la consommation humaine a été fixée à 10 µg/L par l'Organisation Mondiale de la Santé. Une unité de traitement biologique d'eaux potabilisable faiblement arséniée (As< 50µg/L), couplée à une unité de piégeage de l'As en sortie du bioréacteur, a été mise en œuvre sur un site réel afin d'étudier la robustesse du bioprocédé en conditions réelle. Ce bioréacteur à lit fixé a été préalablement ensemencé par une souche bactérienne As(III) oxydante autotrophe (Thiomonas arsenivorans) (Battaglia-Brunet et al., 2002) puis alimenté par l'eau issue du forage dans des conditions de température ambiante (15-17°C). Le suivi du développement du biofilm As(III) oxydant au cours du traitement biologique, par la recherche des gènes codant l'ARNr 16S et une arsenite oxydase (aoxB), a montré une colonisation par des bactéries endogènes de l'eau à traiter. Le rendement d'oxydation de l'étape d'oxydation biologique est compris entre 88 et 100 % avec des concentrations résiduelles en As en sortie du procédé complet (oxydation biologique + piégeage) inférieures à 1 µg/L, qui sont très encourageants pour une application industrielle

Biological As(III) Oxidation Coupled with As(V) Interception by Fibrous Anion Exchange Material FFA-1

International audienceA combined process, including As(III) oxidation and As removal by the fibrous anion exchange material FFA-1, was established to treat arsenite ([As(III)] = 10 mg L−1)-polluted groundwater. Both fixed-bed reactors (R1 and R2) were separately filled with pozzolana and FFA-1. After 72 h of inoculation and 10 days of operation, As(III) oxidation efficiency reached around 100% and the total As in the effluent was below 10 µg L−1 for over 100 days. Then, the combined system was stopped and a desorption experiment on the FFA-1 collected from R2 was carried out. The results revealed that the As trapped by the FFA-1 was distributed linearly along the axial length of R2, and the maximum capacity for removal of the FFA-1 from R2 was about 28 mg As g−1 FFA-1. Moreover, the anions’ competing test showed that they were preferentially sequestrated by the FFA-1 according to the following order: SO42− > PO43− ≈ AsO43− > NO3− at neutral pH. Furthermore, the microorganisms attached to the FFA-1, including some arsenite-oxidizing microorganisms (AsOBs), could be a beneficial complement to the As(III) oxidation and, thus, the total As removal. At the same time, the regeneration test proved that the As(V) interception capacity of FFA-1 was barely affected by the presence of biofilm. Additionally, the calculated operating cost showed that this combined process has great potential for the remediation of As-polluted groundwater

Antiviral Drug Discovery Strategy Using Combinatorial Libraries of Structurally Constrained Peptides

We have developed a new strategy for antiviral peptide discovery by using lyssaviruses (rabies virus and rabies-related viruses) as models. Based on the mimicry of natural bioactive peptides, two genetically encoded combinatorial peptide libraries composed of intrinsically constrained peptides (coactamers) were designed. Proteomic knowledge concerning the functional network of interactions in the lyssavirus transcription-replication complex highlights the phosphoprotein (P) as a prime target for inhibitors of viral replication. We present an integrated, sequential drug discovery process for selection of peptides with antiviral activity directed against the P. Our approach combines (i) an exhaustive two-hybrid selection of peptides binding two phylogenetically divergent lyssavirus P's, (ii) a functional analysis of protein interaction inhibition in a viral reverse genetic assay, coupled with a physical analysis of viral nucleoprotein-P complex by protein chip mass spectrometry, and (iii) an assay for inhibition of lyssavirus infection in mammalian cells. The validity of this strategy was demonstrated by the identification of four peptides exhibiting an efficient antiviral activity. Our work highlights the importance of P as a target in anti-rabies virus drug discovery. Furthermore, the screening strategy and the coactamer libraries presented in this report could be considered, respectively, a general target validation strategy and a potential source of biologically active peptides which could also help to design pharmacologically active peptide-mimicking molecules. The strategy described here is easily applicable to other pathogens

Hemoperitoneum presenting with the use of a topical hemostatic agent in oocyte retrieval: a case report

<p>Abstract</p> <p>Introduction</p> <p>Hemoperitoneum may occur from an ovarian puncture point after oocyte retrieval.</p> <p>Case presentation</p> <p>We report a case of massive hemoperitoneum following transvaginal ultrasound-guided oocyte retrieval in a 33-year-old Caucasian woman. The bleeding required emergency laparoscopy because of active bleeding from the ovarian puncture point. Hemostasis was very difficult to achieve, and traditional operative procedures were not efficient. The only way to stop the bleeding was by using an absorbable fibrinogen and thrombin sealant sponge, which was applied around the ovary. During laparoscopy three pints of packed red blood were administered. No specific alteration of screening coagulation tests was found one month later.</p> <p>Conclusions</p> <p>Hemostasis can be very difficult to achieve with traditional operative procedures. Topical hemostatic agents can be useful to preserve the ovary wherever possible.</p

The genome sequence of the model ascomycete fungus Podospora anserina.

ABSTRACT: BACKGROUND: The dung-inhabiting ascomycete fungus Podospora anserina is a model used to study various aspects of eukaryotic and fungal biology, such as ageing, prions and sexual development. RESULTS: We present a 10X draft sequence of P. anserina genome, linked to the sequences of a large expressed sequence tag collection. Similar to higher eukaryotes, the P. anserina transcription/splicing machinery generates numerous non-conventional transcripts. Comparison of the P. anserina genome and orthologous gene set with the one of its close relatives, Neurospora crassa, shows that synteny is poorly conserved, the main result of evolution being gene shuffling in the same chromosome. The P. anserina genome contains fewer repeated sequences and has evolved new genes by duplication since its separation from N. crassa, despite the presence of the repeat induced point mutation mechanism that mutates duplicated sequences. We also provide evidence that frequent gene loss took place in the lineages leading to P. anserina and N. crassa. P. anserina contains a large and highly specialized set of genes involved in utilization of natural carbon sources commonly found in its natural biotope. It includes genes potentially involved in lignin degradation and efficient cellulose breakdown. CONCLUSION: The features of the P. anserina genome indicate a highly dynamic evolution since the divergence of P. anserina and N. crassa, leading to the ability of the former to use specific complex carbon sources that match its needs in its natural biotope

Autophagy in osteoblasts is involved in mineralization and bone homeostasis

Bone remodeling is a tightly controlled mechanism in which osteoblasts (OB), the cells responsible for bone formation, osteoclasts (OC), the cells specialized for bone resorption, and osteocytes, the multifunctional mechanosensing cells embedded in the bone matrix, are the main actors. Increased oxidative stress in OB, the cells producing and mineralizing bone matrix, has been associated with osteoporosis development but the role of autophagy in OB has not yet been addressed. This is the goal of the present study. We first show that the autophagic process is induced in OB during mineralization. Then, using knockdown of autophagy-essential genes and OB-specific autophagy-deficient mice, we demonstrate that autophagy deficiency reduces mineralization capacity. Moreover, our data suggest that autophagic vacuoles could be used as vehicles in OB to secrete apatite crystals. In addition, autophagy-deficient OB exhibit increased oxidative stress and secretion of the receptor activator of NFKB1 (TNFSF11/RANKL), favoring generation of OC, the cells specialized in bone resorption. In vivo, we observed a 50% reduction in trabecular bone mass in OB-specific autophagy-deficient mice. Taken together, our results show for the first time that autophagy in OB is involved both in the mineralization process and in bone homeostasis. These findings are of importance for mineralized tissues which extend from corals to vertebrates and uncover new therapeutic targets for calcified tissue-related metabolic pathologies