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Four streams flowing in the Iglesiente and Arburese mine districts (SW Sardinia, Italy), exploited for zinc (Zn) and lead (Pb) extraction from sulphides and secondary non-sulphide mineralization (calamine ores), have been studied combining investigations from the macroscale (hydrologic tracer techniques) to the microscale (X-ray powder diffraction, scanning electron microscopy, X-ray absorption spectroscopy). In the investigated area, concerns arise from release of metals to water during weathering of ore minerals and mine-waste. Specifically, Zn is observed at extremely high concentrations (10s of mg/L or more) in waters in some of the investigated catchments. The results from synoptic sampling campaigns showed marked differences of Zn loads, from 6.3 kg/day (Rio San Giorgio) to 2000 kg/day (Rio Irvi). Moreover, natural attenuation of metals was found to occur i) through precipitation of Fe compounds (Fe oxy/hydroxides and “green rust”), ii) by means of the authigenic formation of metal sulphides promoted by microbial sulphate reduction, iii) by metal intake in roots and stems of plants (Phragmites australis and Juncus acutus) and by immobilization in the rhizosphere, and iv) by cyanobacterial biomineralization processes that lead to formation of Zn-rich phases (hydrozincite and amorphous Zn-silicate). The biologically mediated natural processes that lead to significant abatement and/or reduction of metal loads, are the response of environmental systems to perturbations caused from mine activities, and can be considered part of the resilience of the system itself. The aim of this study is to understand the effect of these processes on the evolution of the studied systems towards more stable and, likely, resilient conditions, e.g. by limiting metal mobility and favouring the improvement of the overall quality of water. The understanding of how ecosystems adapt and respond to contamination, and which chemical and physical factors control these natural biogeochemical barriers, can help to plan effective remediation actions.

International audience; Silica phytoliths from the leaves of Setaria vulpiseta (Lam.) Roem. & Schult growing spontaneously on gold-mine contaminated soil were extracted using the Environmental Protection Agency (EPA) 3052 method (HNO3+HCl+HF) and analyzed for Cu, Zn, and As content. The leaves of the plants and the soil were also analyzed for Cu, Zn, Cr, Ni, and As content by the EPA-3050 method (HNO3). The main objective was to determine the amounts of heavy metals present in the soil and organic part of the leaves and inside the structure of the silica phytoliths. The results show that the silica phytoliths comprise 3.9 % of the dry matter of leaves, and retain and store considerable amounts of heavy metals, especially Cu. In addition, we demonstrate that when the metals are estimated by the conventional acid digestion method (without HF), the amounts of metals absorbed by the plants are under-estimated because the silica phytoliths are not dissolved. Therefore, it is necessary to add the amounts of heavy metals found inside the phytoliths to the total amounts found in the organic part of the leaves. The silica phytoliths have high ability to sequester metals and make them unavailable in the environment. Our study should help in developing phytoremediation strategies using plants with high amounts of phytoliths.

Following the recent establishment of the formalism of vectorial ptychography [Ferrand et al., Opt. Lett. 40, 5144 (2015)], first measurements are reported in the optical range, demonstrating the capability of the proposed method to map the four parameters of the Jones matrix of an anisotropic specimen, and therefore to quantify a wide range of optical material properties, including power transmittance, optical path difference, diattenuation, retardance, and fast-axis orientation., Comment: 5 figures, accepted for publication in Optics Letters

Biomineralizacija je složen skup biokemijskih i fizioloških procesa pomoću kojih živi organizmi stvaraju čvrste strukture - biominerale. U morskim organizmima procesi biomineralizacije započinju u ranim embrionalnim razvojnim stadijima, odvijaju se tijekom čitavog životnog ciklusa, a očituju se u kalcifikaciji, dekalcifikaciji i polimorfnim promjenama minerala u tkivima, ljušturama ili skeletima. Proces biomineralizacije ovisi o unutarnjoj aktivnosti organizma, te utjecajima okoliša. Jedan od enzima koji sudjeluju u procesu biomineralizacije je ugljična anhidraza koja katalizira reakciju hidratacije i dehidracije \(CO_2\). Proučavanje mehanizama biomineralizacije je jako popularno zbog široke primjene minerala nastalih tim procesom., Biomineralization is a complex combination of biochemical and physiological processes, during which living organisms produce solid structures - biominerals. In marine organisms, biomineralization processes begin in early embryonic developmental stages and occur throughout the entire life cycle, which is manifested in calcification, decalcification and polymorphic changes of minerals in tissues, shells or skeletons. The biomineralization process depends on endogenous activity of an organism and the exogenous environmental influence. One of the enzymes involved in the biomineralization process is carbonic anhydrase that catalyzes the reaction of hydration and dehydration of \(CO_2\). Biomineralization mechanisms are very popular because of the wide application of minerals created by this process.

The shell of the bivalve mollusc Pinctada maxima is composed of the calcium carbonate polymorphs calcite and aragonite (nacre). Mother‐of‐pearl, or nacre, induces vertebrate cells to undergo osteogenesis and has good osteointegrative qualities in vivo. The calcite counterpart, however, is less researched in terms of the response of vertebrate cells. This study shows that isolation of calcite surface topography from the inherent chemistry allows viable long‐term culture of bone marrow derived mesenchymal stem cells (MSCs). Self‐renewal is evident from the increased gene expression of the self‐renewal markers CD63, CD166, and CD271 indicating that cells cultured on the calcite topography maintain their stem cell phenotype. MSCs also retain their multipotency and can undergo successful differentiation into osteoblasts and adipocytes. When directed to adipogenesis, MSCs cultured on prism replicas are more amenable to differentiation than MSCs cultured on tissue culture polystyrene indicating a higher degree of plasticity in MSCs growing on calcite P. maxima prismatic topography. The study highlights the potential of the calcite topography of P. maxima as a biomimetic design for supporting expansion of MSC populations in vitro, which is of fundamental importance if it meets the demands for autologous MSCs for therapeutic use.

Although biomineralization in plants is an important area of research, there is very limited information. In this work, we report the location of Na, K, Ca, Mg and Fe biominerals in Sarcocornia pruinosa (Chenopodiacaeae), a halophyte species growing in the estuarine area of Río Tinto, an extreme acidic environment. The estuarine soils of the Tinto basin are characterized by slightly acidic pH and high concentrations of ions. They are exposed to Atlantic Ocean tides that contribute to the increase in pH, Na and Mg concentrations. The aim of this work was to characterize the elemental composition and to identify the biominerals detected in cell tissues of S. pruinosa. Analytical techniques, such as ICP-MS (Inductively coupled plasma mass spectrometry), XRD and microscopy such as OM (optical microscopy) with histochemical staining, SEM and TEM (scanning and transmission electronic microscopy) coupled with EDX (energy dispersive X-ray) were carried out to analyze the plant tissues of S. pruinosa and characterize the detected biominerals. The elemental composition in succulent stems and seeds of S. pruinosa showed high values of Na and K followed by Ca, Mg and Fe. The presence of halite, sylvite, weddellite, glushinskite and Fe oxides biominerals in this halophyte species is reported. Our data suggest the importance of vegetation in the biogeochemical cycles in estuarine areas., Ministerío de Economía y Competitividad

Biominerals are all the minerals produced by living organisms. They are essential materials, present in almost all living species. Nevertheless,the structural, chemical properties and, formation mechanisms and the evolution of these materials are still heavily debated. This is due in particular to thedifficulties of experimentally studying chemical species evolving in biologicalenvironments. Although, equally complex, a theoretical approach at the molecular level can help in the characterization of these biological materialsand in particular the characterization of their interfaces formed with the surrounding biological media. This is essential for a better understandingof the formation and evolution of these minerals.Calcium oxalates are essential biominerals that are very common in the living world. They constitute the main crystalline speciesencountered in kidney stones where they can exist in three phases possessing different degrees of hydration. In this, thesis we carried outsimulations to predict the IR and NMR spectroscopic properties of these three phases. Thsi enabled us to obtain specificsignature of each polyhydrate, and thus makes it possible to obtain a signature specific to each of them, thus helpingthe identification of these phases from the experimentally spectra obtained.Calcium phosphates are part of the bio/biological minerals. They make up the major part of the bone mineral of mammals. This mineral is in the form of nanoparticles havinga crystalline core of hydroxyapatite and a hydrated and disordered surface layer.During this thesis we were interested in these two components. Concerning the crystalline core of the particles, we studied in particularthe case of carbonate substitutions because of its predominant substitution in biological apatites. By combining this work with solid state NMR experimentswe can propose a precise localization of these substituents within the hydroxyapatite crystalline cell.The disordered surface layer is still very poorly understood and many structural models are proposed in the literature to describe it. We haveconsidered a number of them for which we have modeled the NMR properties which were then confronted with experimental results. The comparaisonmade it possible to identify the strengths and weaknesses of the various hypotheses.; On appelle biominéraux l’ensemble des minéraux fabriqués par le vivant. Ce sont des matériaux essentiels, présents dans la quasi-totalitédes espèces vivantes. Néanmoins les caractéristiques structurales, chimiques ainsi que les mécanismes de formation, et l’évolution de cesmatériaux sont encore fortement débattus. Cela s’explique notamment par les difficultés à étudier expérimentalement des espèces chimiquesévoluant en milieux biologiques.Bien que tout aussi complexe, une approche théorique, à l’échelle moléculaire, peut aider à la caractérisation de ces matériaux biologiqueset notamment la caractérisation de leurs interfaces formées avec les milieux biologiques environnants. Cela étant essentiel pour une meilleurecompréhension de la formation et de l’évolution de ces minéraux.Les oxalates de calcium constituent une famille de biominéraux très importante dans le monde du vivant. Ils constituent notamment les principales espèces cristallinesrencontrées dans les calculs rénaux où ils peuvent exister sous trois phases possédant différents degrés d'hydratation. Au cours de cette thèse, nous avons effectuéles simulations des propriétés spectroscopique IR et RMN des ces trois phases, ce qui permet d'obtenir une signature propre à chacune d'entre elle, aidant ainsi àl'identification de ces phases à partir des spectres obtenus expérimentalement.Les phosphates de calcium font aussi partie des biominéraux. Ils composent la majeure partie du minéral osseux des mammifères. Ce minéral se trouvesous la forme de nanoparticules décrites comme possédant un cœur cristallin d’hydroxyapatite substituées entourée d'une couche hydratée et désordonnée en surface.Durant ce travail de thèse, nous nous sommes intéressés à ces deux composantes. Concernant le cœur cristallin des particules, nous avons étudié en particulierle cas des substitutions par des carbonates car il s'agit de la substitution prédominante dans les apatites biologiques. En couplant ce travail à des expériencesde RMN solide nous pouvons proposé une localisation précise de ces substituants au sein de la maille d’hydroxyapatite.La couche désordonnée de surface est encore très mal comprise à l'heure actuelle et de nombreux modèles structuraux sont proposés dans la littérature pour la décrire. Nous avonsconsidéré un certain nombre d'entre eux pour lesquels nous avons modélisé les propriétés RMN, qui confrontées à celle issues de l'expérience nous ontpermis d'identifier les points forts et faibles des différentes hypothèses.

Microbe-mineral interactions in caves can lead to secondary mineral formations such as speleothems, moonmilk etc. In the present review, we provide a summary of geomicrobiological work done so far in some Indian caves. Microbially induced mineralization is documented in cave ecosystems and microbial metabolisms help in mineral formations either through direct/active or indirect/passive processes. Laboratory based experiments conducted on speleothems from Sahastradhara caves (Dehradun); Borra Cave (Andhra Pradesh); Krem Phyllut, Krem Mawsmai, Krem Mawmluh and Rongai Dobhakol (Meghalaya) have clearly demonstrated that bacterial strains isolated from these caves have the capability to precipitate minerals under controlled conditions.

Рассматривается возможный механизм формирования зародыша желчного камня. Опираясь на ранее полученные результаты экспериментальных исследований, объясняется возможный механизм воздействия лазерного излучения на процессы кристаллообразования в объеме биологических жидкостей, в частности, в желчи человека.

Dolomite (MgCa(CO3)2) is an important petroleum reservoir rock mineral common in ancient sedimentary rocks which is infrequently found in modern environments. The mechanism of dolomite formation remains poorly understood, although recent research has focused on the contribution of microbial processes. Sabkha is the Arabic term for saline mudflats occurring in regions characterized by extreme environmental conditions (high temperature, salinity, light intensity, and aridity), where diverse halophilic and extremophilic microorganisms are found. The dynamic evaporitic systems characteristic of sabkhas are crucial for the precipitation of minerals and a role for microorganisms in sabkhas in the process of mineralization has been proposed. In this study the Dohat Faishakh Sabkha in Qatar was investigated for evidence of the role for aerobic bacteria in mediating the formation of high magnesium carbonates and dolomite, two minerals that commonly occur in the sabkha sediments. Twenty-nine strains of aerobic microbes were obtained through inoculation on agar plates from two different cores sampled from the sabkha and identified by 16S rRNA gene sequencing as belonging to the genera Bacillus, Salinivibrio, Staphylococcus and, primarily, Virgibacillus. All strains examined caused the pH of an artificial growth medium to increase from 7 to 8.5; however, not all were capable of mediating mineral formation. Only Salinivibrio and Virgibacillus spp. isolates mediated the formation of detectable solid phases within the agar plates. Light microscopy, scanning electron microscopy energy dispersive X-ray (SEM/EDX), and X-ray diffraction (XRD) analyses indicate that the solid phase produced in the presence of these bacterial strains is MgCa(CO3)2 with a MgCO3 mol% varying from 0 to 40%. The results of these laboratory experiments suggested that, in the Dohat Faishakh Sabkha, aerobic bacteria may contribute in the formation of very high Mg calcite, a mineral that is considered the precursor of ordered dolomite., Frontiers in Environmental Science, 5, ISSN:2296-665X

Nature successfully employs inorganic solid-state materials (i.e., biominerals) and hierarchical composites as sensing elements, weapons, tools, and shelters. Optimized over hundreds of millions of years under evolutionary pressure, these materials are exceptionally well adapted to the specifications of the functions that they perform. As such, they serve today as an extensive library of engineering solutions. Key to their design is the interplay between components across length scales. This hierarchical design—a hallmark of biogenic materials—creates emergent functionality not present in the individual constituents and, moreover, confers a distinctly increased functional density, i.e., less material is needed to provide the same performance. The latter aspect is of special importance today, as climate change drives the need for the sustainable and energy-efficient production of materials. Made from mundane materials, these bioceramics act as blueprints for new concepts in the synthesis and morphosynthesis of multifunctional hierarchical materials under mild conditions. In this review, which also may serve as an introductory guide for those entering this field, we demonstrate how the pursuit of studying biomineralization transforms and enlarges our view on solid-state material design and synthesis, and how bioinspiration may allow us to overcome both conceptual and technical boundaries.

Self-organized precipitation structures might hold the key to a new microengineering paradigm that grows materials biomimetically., Far from the thermodynamic equilibrium, many precipitation reactions create complex product structures with fascinating features caused by their unusual origins. Unlike the dissipative patterns in other self-organizing reactions, these features can be permanent, suggesting potential applications in materials science and engineering. We review four distinct classes of precipitation reactions, describe similarities and differences, and discuss related challenges for theoretical studies. These classes are hollow micro- and macrotubes in chemical gardens, polycrystalline silica carbonate aggregates (biomorphs), Liesegang bands, and propagating precipitation-dissolution fronts. In many cases, these systems show intricate structural hierarchies that span from the nanometer scale into the macroscopic world. We summarize recent experimental progress that often involves growth under tightly regulated conditions by means of wet stamping, holographic heating, and controlled electric, magnetic, or pH perturbations. In this research field, progress requires mechanistic insights that cannot be derived from experiments alone. We discuss how mesoscopic aspects of the product structures can be modeled by reaction-transport equations and suggest important targets for future studies that should also include materials features at the nanoscale.

Cataloged from PDF version of article. Includes bibliographical references (leaves 59-68). Thesis (M.S.): Bilkent University, Department of Materials Science and Nanotechnology, İhsan Doğramacı Bilkent University, 2016. Nature has been an inspiration and information source for scientists over centuries, for developing new materials. A great e ort has been spent in order to understand biological materials. The biomineralization process is observed in the nature and it creates perfectly hierarchical structures, which give the living organisms extraordinary properties. It is also a fact that along with the nature; living creatures such as nacre and bacteria employ biomineralization in order to produce minerals for protection and navigation purposes. In addition, bone is a composite material which protects the internal organs and provides mechanical support and is a result of biomineralization process. In this thesis, the biomineralization processes of living organisms and bone is mimicked by employing peptide amphiphile nano bers as templates for inorganic materials production. Glutamic acid residue is used in order the mimic the negatively charged domains for proteins, which play crucial roles in biomineralization process in some organisms and bone. In order to mimic the structure of sea shell, which is composed of calcium carbonate, and bone, which consists of calcium phosphate, relevant mineral solutions were used. In conclusion, when organic and inorganic components are used together, they demonstrate superior mechanical properties, when compared to organic molecules alone. by Egemen Deniz Eren. M.S.

Метою роботи є проведення огляду сучасних технологій, що базуються на біохімічному методі очищення підземних вод, а також визначенням його переваг у порівнянні з традиційними технологіями; показ перспективності використання даного методу в сучасному світі; огляд шляхів інтенсифікації біохімічного методу очищення підземних вод. Відзначено, що в сучасних умовах актуальним завданням інтенсифікації роботи існуючих станцій знезалізнення або тих, що проектуються, є переведення їх із екстенсивних технологій до технологій, які забезпечують високу швидкість окиснення сполук заліза, ведуть до зменшення обсягів промивних вод, збільшення тривалості фільтроциклу, покращення умов експлуатації, зменшення капітальних та експлуатаційних витрат. Керуючись результатами досвіду використання даного методу в сучасному світі, встановлено, що він є одним із можливих напрямків інтенсифікації роботи станцій знезалізнення. Подано деякі технологічні схеми, їх основні технологічні параметри. Вказано оптимальні межі розвитку залізобактерій, структури їхніх капсул. На підставі огляду досліджень показана різниця між структурою та фізико-хімічними властивостями осаду, що утворюється в результаті використання традиційних фізико-хімічних методів і біологічного методу знезалізнення. Подано розроблені автором технології та вказана їхня відмінність від існуючих. Визначено основні відмінності між біологічними й традиційними фізико-хімічними методами знезалізнення. The purpose of this paper is to review the latest technologies based on biochemical method of purification of groundwater, as well as the definition of its advantages over traditional technologies. The prospects of using this method in the modern world and the ways of intensification of the biochemical method of purification of groundwater are considered. It is noted that in the present conditions an important task of intensification of existing or newly designed iron removal stations, is to transfer them from the extensive technologies to technologies that provide a high rate of oxidation of iron compounds, lead to a decrease in the volume of wash water, an increase in the duration of the filtration cycle, improve operating conditions, a decrease in capital and operating costs. Based on the results of the experience review as for using this method in the modern world, it is recognized that it is one of the possible directions of intensification at iron removal stations. Technological schemes and parameters are also given. The optimal conditions of iron bacteria life cycle , structure of their capsule are represented . Based on a review of research the difference between the structure and physicochemical properties of sewage sludge, resulting from the use of traditional physical and chemical methods, and biological iron removal method is shown. These technologies, developed by the author. It is shown how they differ from existing technologies. The main differences between the biological and conventional physical and chemical methods of iron removal are discussed. Целью данной работы является проведение обзора современных технологий, базирующихся на биохимическом методе очистки подземных вод, а так же определение его преимуществ над традиционными технологиями. Показана перспективность использования данного метода в современном мире. Рассмотрены пути интенсификации биохимического метода очистки подземных вод. Отмечено, что в современных условиях актуальной задачей интенсификации работы существующих или вновь проектируемых станций обезжелезивания, является перевод их из экстенсивных технологий к технологиям, которые обеспечивают высокую скорость окисления соединений железа, ведут к уменьшению объемов промывных вод, увеличению продолжительности фильтроцикла, улучшению условий эксплуатации, уменьшению капитальных и эксплуатационных расходов. Опираясь на результаты обзора опыта использования данного метода, в современном мире, установлено, что он является одним из возможных направлений интенсификации работы станций обезжелезивания. Приведены некоторые технологические схемы, их основные технологические параметры. Приведены оптимальные границы развития железобактерий, структуры их капсул. На основании обзора исследований показана разница между структурой и физико-химическими свойствами осадков, образующихся в результате использования традиционных физико-химических методов, и биологического метода обезжелезивания. Приведенные технологии, разработанные автором. Показано их отличие от существующих технологий. Приведены основные различия между биологическими и традиционными физико-химическими методами обезжелезивания.

International audience; Humans have intentionally used biological materials such as bone, ivory and shells since prehistoric times due to their particular physical and chemical properties. The composite nature of biological materials at the nanoscale combined with an important structural hierarchy up to the macroscopic level is responsible for these exceptional properties. In this chapter we discuss the relation of the structural features of different biological materials within their archaeological and historical contexts along with their anthropological use and function. Amid the wealth of biological materials of archaeological interest, a special attention is paid to carbonate-based materials such as corals and shells and phosphate-based ones, including bone, teeth, ivory and antler. The structural features of these archaeobiominerals at different length scales down to the nanoscopic scale are highlighted in this chapter as they allow drawing conclusions on ancient working techniques, the provision and circulation of raw materials, anthropological heat processes, and, last but not least, on diagenetic changes and authentication purposes. The informative potential of observations of archaeological biological materials at different length scales is finally illustrated by some study cases.

International audience; The detection and identification of carbonates on Mars are of prime importance to establish the evolution of its atmosphere, correlated to the history of the liquid water, or even to determine the existence of a possible ancient biological activity. To date, no large deposits of carbonates have been found. In fact, their detection is specific to local areas and in very low amounts. The absence of such deposits is commonly attributed to the harsh environmental conditions at the surface of Mars. Additionally, the presence of UV radiation has been proposed to explain their photodecomposition and hence their absence. However, contradictory results from laboratory experiments mimicking Mars' surface UV radiation did not resolve the behaviour of carbonates in such an environment, which is why we exposed, in low Earth orbit and in laboratory experiments, both abiotic and biotic calcium carbonates to UV radiation of wavelength above 200 nm, the same spectral distribution as the one reaching the surface of Mars. For low Earth orbit (LEO) exposure, this was done for the UVolution experiment on board the BIOPAN ESA module, which was set outside a Russian Foton automated capsule, and exposed to space conditions for 12 days in September 2007. The targeted carbonates are biominerals and abiotic samples. Our laboratory results mainly show that the exposed carbonates appear to be stable to UV radiation if directly exposed to it. The LEO experiment results tend to the same conclusion, but the integrated exposition time to Solar UV during the experiment is not sufficient to be conclusive. However, the stability of the biominerals derived from the laboratory experiment could strengthen the interest to explore deeper their potential as life records at Mars. Hence, they should be considered as primary targets for in situ analyses during future missions.

Mesocrystals are 3D ordered nanoparticle superstructures, often with internal porosity, which receive much recent research interest. While more and more mesocrystal systems are found in biomineralization or synthesized, their potential as material still needs to be explored. It needs to be revealed, which new chemical and physical properties arise from the mesocrystal structure, or how they change by the ordered aggregation of nanoparticles to fully exploit the promising potential of mesocrystals. Also, the mechanisms for mesocrystal synthesis need to be explored to adapt it to a wide class of materials. The last three years have seen remarkable progress, which is summarized here. Also potential future directions of this reaserch field are discussed. This shows the importance of mesocrystals not only for the field of materials research and allows the appliction of mesocrystals in advanced materials synthesis or property improvement of existing materials. It also outlines attractive research directions in this field.

In metazoans, the secretion of skeletal calcium carbonate tissues is regulated by a complex array of extracellular macromolecules, namely proteins and polysaccharides, and sometimes lipids that collectively constitute the skeletal matrix. Because of its ability to ‘sculpt’ the biominerals and to organize spatially crystallites in well-defined microstructures, this matrix has been the focus of several studies. In the last few years, by using proteomics alone or by merging transcriptomics and proteomics, there has been a wealth of information obtained on the protein moieties of the skeletal matrix, in different model and non-model organisms: corals, molluscs, brachiopods, sea urchins. These data allow now establishing preliminary comparisons between the ‘molecular kits’ of different species, from phylum to phylum, and within one given phylum. The obtained data show a remarkable diversity of the proteins involved in mineral deposition, in term of primary structures and of putative functions deduced from in silico sequence analysis. This diversity invites to refine the existing molecular models of mineral deposition and to integrate the role of the calcifying epithelium/calcifying cells facing the front of mineral growth. As illustrated by molluscan nacre on the one hand, and by examples taken from other phyla on the other hand, it appears that ‘similar’ microstructures may emerge from very different protein ‘toolkits’ ; this finding puts into question past attempts to use the matrix for taxonomic purposes. It reveals the astonishing plasticity of the ‘calcifying matrix’ and emphasizes the fact that it is built by the co-option of ancient and recent functions. In a counterintuitive manner, proteomic data suggest that the skeletal matrix is less evolutionary constrained than suspected, exhibits a true ‘evolvability’, while maintaining stable and perennial the associated microstructures.

Early diagenetic changes occurring in aragonite coral skeletons were characterized at the micro- and ultra-structural scales in living and fossil scleractinian colonies, the latter of Pleistocene age. The skeleton of scleractinian corals, like all biomineralized structures, is a composite material formed by the intimate association of inorganic aragonite crystallites and organic matrices. In addition to its organo-mineral duality, the scleractinian skeleton is formed by the three-dimensional arrangement of two clearly distinct basic structural features, the centers of calcification and the fibers. The latter are typically characterized by a transverse micron-scale zonation revealing their incremental growth process. The size, geometry and three-dimensional arrangement of calcification centers and fibers are taxon-specific. The earliest diagenetic modifications of these skeletons have been clearly recognized in the older parts of living colonies. The first steps of diagenesis therefore take place only a few years after the skeleton had been secreted by the living polyps, and in the same environmental conditions. Comparisons with the uppermost living parts of the coral colonies clearly show that these first diagenetic changes are driven by the biological ultrastructural characteristics of these skeletons and are conditioned by the presence of organic envelopes interbedded with and surrounding aragonite crystallites. These first diagenetic processes induce the development of thin fringes of fibrous aragonite cements growing syntaxially on the aragonitic coral fibers, an alteration of the incremental zonation of coral fibers and also preferential diagenetic changes in the calcification centers, including dissolution of their minute internal crystals. Diagenetic patterns observed in Pleistocene coral colonies typically involve the same processes already recognized in the older skeletal parts of living colonies, suggesting that diagenesis occurs through continuous processes instead of clearly differentiated stages. Selective dissolution affects calcification centers and some growth increments of coral fibers. Alteration of the initial transverse zonation of coral fibers also occur through the development of micro-inclusions clearly seen in ultra-thin sections. Although usually thicker than those observed in the ancient skeletal parts of living colonies, syntaxial aragonite cements commonly occur in these fossil skeletons. These cements are often associated with gradual textural modifications of the underlying coral fibers, in particular the loss of the transverse micron-scale zonation. This suggests that the coral skeleton forming the substratum of diagenetic cements is progressively recrystallized in secondary aragonite. This recrystallization of coral aragonite begins at the external margin of the skeleton, just below the diagenetic cements and gradually moves towards the internal skeletal parts. Recrystallization takes place through concomitant fine-scale dissolution-precipitation processes and occurs with textural changes but no mineralogical change. The process of recrystallization is likely initiated by a biological degradation of organic skeletal matrices and can be also driven by thermodynamical constraints involving the lowering of surface free energies resulting from changes in crystal size. Alteration of skeletal organic matrix, textural changes in coral biocrystals through recrystallization and precipitation of secondary diagenetic aragonite may bias the original geochemical characteristics of coral skeletons. Although more work is needed to establish the influence of these early diagenetic processes on the geochemical signatures, it is already well known that the breakdown of organic skeletal envelopes and early recrystallization of shallow-water carbonates alter the stable isotopic composition. The widespread use of coral skeletons as environmental and climatic proxies makes strongly necessary a better understanding of these early diagenetic mechanisms and a precise characterization of the fine-scale diagenetic patterns of specimens for the optimization of geochemical interpretations. In particular, it cannot be assumed that an entire aragonitic composition can guarantee that there is no or slight diagenetic alteration.

Species of Haliotis (abalone) show high variety in structure and mineralogy of the shell. One of the European species (Haliotis tuberculata) in particular has an unusual shell structure in which calcite and aragonite coexist at a microscale with small patches of aragonite embedded in larger calcitic zones. A detailed examination of the boundary between calcite and aragonite using analytical microscopies shows that the organic contents of calcite and aragonite differ. Moreover, changes in the chemical composition of the two minerals seem to be gradual and define a micrometric zone of transition between the two main layers. A similar transition zone has been observed between the layers in more classical and regularly structured mollusk shells. The imbrication of microscopic patches of aragonite within a calcitic zone suggests the occurrence of very fast physiological changes in these taxa.

Limpets (Gastropoda) and chitons (Polyplacophora) feed on epi- and endolithic organisms by means of the radula, a specialized feeding apparatus located in the mouth cavity. The radula owes most of its abrasive capability to the presence of numerous mineralized teeth. Here we report on the shape, internal structure, wearing pattern, feeding position, and distribution of hardness and elastic properties of these teeth in an attempt to generate ideas for the innovation of industrial cutting devices. The teeth remain sharp during their entire working-life mainly due to the fact that wearing preferentially occurs along surfaces formed by the internal structure of the tooth. It is shown that shape, internal structure, positioning and material characteristics concertedly function in minimizing the rate at which the teeth wear down and in maintaining optimal cutting behaviour. Implementation of these self-sharpening characteristics into industrial cutting devices is discussed. (C) 2000 Elsevier Science S.A. All rights reserved.

Limpets (Gastropoda) and chitons (Polyplacophora) feed on epi- and endolithic organisms by means of the radula, a specialized feeding apparatus located in the mouth cavity. The radula owes most of its abrasive capability to the presence of numerous mineralized teeth. Here we report on the shape, internal structure, wearing pattern, feeding position, and distribution of hardness and elastic properties of these teeth in an attempt to generate ideas for the innovation of industrial cutting devices. The teeth remain sharp during their entire working-life mainly due to the fact that wearing preferentially occurs along surfaces formed by the internal structure of the tooth. It is shown that shape, internal structure, positioning and material characteristics concertedly function in minimizing the rate at which the teeth wear down and in maintaining optimal cutting behaviour. Implementation of these self-sharpening characteristics into industrial cutting devices is discussed. (C) 2000 Elsevier Science S.A. All rights reserved.

International audience; To assess the effect of polymeric substances on the biomineralization and stabilization of green rust (GR), the effect of two organic polymers on the transformation of lepidocrocite (γ-FeOOH) to GR vs. magnetite in presence of Shewanella putrefaciens was investigated. These two polymers, generally used as flocculants, are polyacrylic acid (PAA), which bears negatively charged carboxylic groups at neutral pH and is expected to react with cationic hydrolyzed iron species, and polyacrylamide (PAM), which is a neutral polymer that may develop hydrogen bonds with iron nanocolloids. The bioreduction of lepidocrocite by S. putrefaciens was performed under conditions known to yield either magnetite or GR. Each operational condition of interest was investigated with various polymer concentrations from 0.6 to 60 mg g−1 Fe (10 to 1000 mg l−1). The final product was characterized using X-ray diffraction and electronic microscopy. The results showed that the formation of GR is favored, with respect to magnetite, to a lesser extent with PAM than with PAA. These results indicated that polymers influence the chemical stability of GR and/or guide the route of biomineralization. Polymer properties, in addition to silica and phosphate concentrations, are then critical parameters that control the secondary iron mineral biomineralization from iron-reducing bacteria.

Different aspects of biominerals formed by apatite and DNA have been investigated using computer modeling tools. Firstly, the structure and stability of biominerals in which DNA molecules are embedded into hydroxyapatite and fluoroapatite nanopores have been examined by combining different molecular mechanics methods. After this, the early processes in the nucleation of hydroxyapatite at a DNA template have been investigated using molecular dynamics simulations. Results indicate that duplexes of DNA adopting a B double helix can be encapsulated inside nanopores of hydroxyapatite without undergoing significant distortions in the inter-strand hydrogen bonds and the intra-strand stacking. This ability of hydroxyapatite is practically independent of the DNA sequence, which has been attributed to the stabilizing role of the interactions between the calcium atoms of the mineral and the phosphate groups of the biomolecule. In contrast, the fluorine atoms of fluoroapatite induce pronounced structural distortions in the double helix when embedded in a pore of the same dimensions, resulting in the loss of its most relevant characteristics. On the other hand, molecular dynamics simulations have allowed us to observe the formation of calcium phosphate clusters at the surface of the B-DNA template. Electrostatic interactions between the phosphate groups of DNA and Ca2+ have been found to essential for the formation of stable ion complexes, which were the starting point of calcium phosphate clusters by incorporating PO3 4 from the solution. This work is integrated within a wider research project supported by B. Braun Surgical S.A., UPC, Institut de Ciencies Fotòniques (ICFO), and the Institut Català de la Salut (ICS) through the H. A. Germans Trias i Pujol and H. U. Vall d’Hebron, MICINN-FEDER funds (MAT2012-34498), and by the Generalitat de Catalunya (2009SGR925 and XRQTC). Authors are indebted to the Centre de Supercomputació de Catalunya (CESCA) for computational facilities. Support for the research of C. A. was received through the “ICREA Academia”.

Black coatings were detected on granite surfaces in groundwater catch work tunnels from Porto city (NW Portugal). XRD, FTIR, Micro-Raman, ICP-MS, TEM-EDS, SEM-EDS and SEM-FIB were the analytical procedures carried out to investigate the origin of the black coatings. In this subterranean environment, the enrichment in metals and other trace elements, such as Mn and Fe, and clay minerals characterize the black microbial mats, mainly composed of Mn/Fe-oxidising bacteria., Fundação para a Ciência e a Tecnologia (FCT)