Mineral formation in the primary polyps of pocilloporoid corals

In reef-building corals, larval settlement and its rapid calcification provides a unique opportunity to study the bio-calcium carbonate formation mechanism involving skeleton morphological changes. Here we investigate the mineral formation of primary polyps, just after settlement, in two species of the pocilloporoid corals: Stylophora pistillata (Esper, 1797) and Pocillopora acuta (Lamarck, 1816). We show that the initial mineral phase is nascent Mg-Calcite, with rod-like morphology in P. acuta, and dumbbell morphology in S. pistillata. These structures constitute the first layer of the basal plate which is comparable to Rapid Accretion Deposits (Centers of Calcification, CoC) in adult coral skeleton. We found also that the rod-like/dumbbell Mg-Calcite structures in subsequent growth step will merge into larger aggregates by deposition of aragonite needles. Our results suggest that a biologically controlled mineralization of initial skeletal deposits occurs in three steps: first, vesicles filled with divalent ions are formed intracellularly. These vesicles are then transferred to the calcification site, forming nascent Mg-Calcite rod/pristine dumbbell structures. During the third step, aragonite crystals develop between these structures forming spherulite-like aggregates

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance.

Investment in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing in Africa over the past year has led to a major increase in the number of sequences that have been generated and used to track the pandemic on the continent, a number that now exceeds 100,000 genomes. Our results show an increase in the number of African countries that are able to sequence domestically and highlight that local sequencing enables faster turnaround times and more-regular routine surveillance. Despite limitations of low testing proportions, findings from this genomic surveillance study underscore the heterogeneous nature of the pandemic and illuminate the distinct dispersal dynamics of variants of concern-particularly Alpha, Beta, Delta, and Omicron-on the continent. Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve while the continent faces many emerging and reemerging infectious disease threats. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Manuel relatif aux matières naturelles pour barrières argileuses ouvragées pour C.E.T. (centres d'enfouissement technique) et réhabilitation de dépotoirs en région wallonne.

La Région wallonne a confié aux laboratoires ci-dessus, la mission de rédiger un manuel technique qui décrit la sélection et la qualification des gisements et des matériaux argileux ainsi que le contrôle de la mise en œuvre des barrières argileuses ouvragées destinées à la réalisation des centres d'enfouissement technique (CET) ou à la réhabilitation de dépotoirs en Région wallonne. CET : Centre d’enfouissement technique, appellation pour les décharges, définies comme installations d’élimination contrôlée où des déchets sont définitivement entreposés sur ou dans le sol. La directive européenne a gardé l’appellation " décharge ". Ce manuel précise les moyens de qualification, de mise en œuvre et de contrôle de barrières étanches rapportées en fond de fouille, sur les flancs, ainsi qu'en couverture sur un site dont le substratum naturel ne satisfait pas aux contraintes environnementales réglementaires. Le matériau doit répondre à différents objectifs, liés à l'obtention d'un coefficient de perméabilité inférieur à 1.10-9m/s in situ, à la stabilité mécanique de l'ouvrage mais aussi au maintien des performances à long terme de la barrière argileuse dans les conditions d'exploitation. Cfr. annexe I de la DIRECTIVE 199/31/CE DU CONSEIL, du 28 avril 1999 En fonction de leurs propriétés, l'utilisation d'argiles (la définition précise du terme argile est donnée dans le manuel) s'impose. Néanmoins, une gamme plus large de matériaux naturels pourrait correspondre aux critères requis. Ainsi, en ce qui concerne la valorisation de sous produits des industries minérales, des boues ou des stériles miniers, la même démarche que celle préconisée pour les matériaux argileux naturels permettra de vérifier s'ils peuvent répondre aux exigences de qualification. Il convient en premier lieu d'apporter la preuve, via un laboratoire agréé, que le matériau ne présente pas de contamination qui le rende impropre à l'usage envisagé. Le manuel est réalisé sur base de l’expérience des auteurs et intègre celle de bureaux de contrôle agréés. Il prend aussi en compte les informations d’études réalisées à l’étranger. La démarche adoptée est de distinguer les différentes étapes de réalisation de la barrière argileuse : choix du matériau (gisement, qualité), définition des méthodes et moyens de mise en œuvre et contrôle in situ (planche d’essai), contrôle des fournitures sur chantier, contrôle final de la barrière étanche

Relation between the Macroscopic Pattern of Elephant Ivory and Its Three-Dimensional Micro-Tubular Network.

Macroscopic, periodic, dark and bright patterns are observed on sections of elephant tusk, in the dentin part (ivory). The motifs-also called Schreger pattern-vary depending on the orientation in the tusk: on sections perpendicular to the tusk axis, a checkerboard pattern is present whereas on sections longitudinal to it, alternating stripes are observed. This pattern has been used to identify elephant and mammoth ivory in archeological artifacts and informs on the continuous tissue growth mechanisms of tusk. However, its origin, assumed to be related to the 3D structure of empty microtubules surrounded by the ivory matrix has yet to be characterized unequivocally. Based on 2D observations of the ivory microtubules by means of a variety of imaging techniques of three different planes (transverse, longitudinal and tangential to the tusk axis), we show that the dark areas of the macroscopic pattern are due to tubules oblique to the surface whereas bright areas are related to tubules parallel to it. The different microstructures observed in the three planes as well as the 3D data obtained by SR-μCT analysis allow us to propose a 3D model of the microtubule network with helical tubules phase-shifted in the tangential direction. The phase shift is a combination of a continuous phase shift of π every 1 mm with a stepwise phase shift of π/2 every 500 μm. By using 3D modeling, we show how the 3D helical model better represents the experimental microstructure observed in 2D planes compared to previous models in the literature. This brings new information on the origin of the unique Schreger pattern of elephant ivory, crucial for better understanding how archaeological objects were processed and for opening new routes to rethink how biological materials are built

Chemical and Structural Insights of the Nano Organo–Mineral Interfaces in Growing Abalone Nacre

International audienceCharacterizing the nano organo–mineral interfaces in nacre is of primary importance to understand the processes of nucleation, growth, orientation, and organization of the aragonite tablets. Here, we investigated these different interfaces in growing nacre of abalone Haliotis tuberculata shell using a combination of advanced techniques, i.e., focused ion beam milling coupled with field emission gun scanning electron microscopy, high-resolution transmission electron microscopy, scanning transmission X-ray microscopy, and electron energy loss spectroscopy. We show the presence of “globules”-like organic-rich inclusions within the center of each tablet that extend from one tablet to another through mineral bridges surrounded by organics. These structures may control the growth of the columnar stacking of tablets supporting different findings from the literature. In the lateral growing surface of the tablets, we reveal the presence of a thick organic domain rich in calcium but deficient in carbonate ions strengthening the idea that calcium-binding acidic proteins are involved in tablet’s lateral growth. Overall, this work emphasizes the importance of nanoscale chemical and structural analysis of the organo–mineral interfaces in growing nacre, allowing in particular for the discrimination between organic and inorganic carbons