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• New method for nanoscale analysis of hydroxyapatite crystallites in dental enamel. • Dynamic template matching method is combined with TKD in the SEM. • Many HAp crystallites have significant internal orientation variation. • Frequent low angle boundaries and possible twin boundaries between crystallites. • Measuring only 〈0001〉 orientations will miss key microstructural features in HAp. The remarkable physical properties of dental enamel can be largely attributed to the structure of the hydroxyapatite (HAp) crystallites on the sub-micrometre scale. Characterising the HAp microstructure is challenging, due to the nanoscale of individual crystallites and practical challenges associated with HAp examination using electron microscopy techniques. Conventional methods for enamel characterisation include imaging using transmission electron microscopy (TEM) or specialised beamline techniques, such as polarisation-dependent imaging contrast (PIC). These provide useful information at the necessary spatial resolution but are not able to measure the full crystallographic orientation of the HAp crystallites. Here we demonstrate the effectiveness of enamel analyses using transmission Kikuchi diffraction (TKD) in the scanning electron microscope, coupled with newly-developed pattern matching methods. The pattern matching approach, using dynamic template matching coupled with subsequent orientation refinement, enables robust indexing of even poor-quality TKD patterns, resulting in significantly improved data quality compared to conventional diffraction pattern indexing methods. The potential of this method for the analysis of nanocrystalline enamel structures is demonstrated by the characterisation of a human enamel TEM sample and the subsequent comparison of the results to high resolution TEM imaging. The TKD – pattern matching approach measures the full HAp crystallographic orientation enabling a quantitative measurement of not just the c-axis orientations, but also the extent of any rotation of the crystal lattice about the c-axis, between and within grains. Results presented here show how this additional information highlights potentially significant aspects of the HAp crystallite structure, including intra-crystallite distortion and the presence of multiple high angle boundaries between adjacent crystallites with rotations about the c-axis. These and other observations enable a more rigorous understanding of the relationship between HAp structures and the physical properties of dental enamel. [ABSTRACT FROM AUTHOR]

• The 'Cloudina tubes ' were synthesized by pulsed electrochemical method. • The origin of Ediacaran tubular fossils and the reconstruction of the Ediacaran marine environment were investigated. • It provides a scientific basis for the study of the origin and evolution of Cloudina tubular fossils and the reconstruction of the Ediacaran marine environment. Tubular fossil Cloudina and other contemporaneous cloudinids from the terminal Ediacaran (∼551–539 Ma) have long been widely regarded as the earliest known metazoans with biomineralisation. During the Ediacaran to Early Cambrian Period, three phosphorous-rich rock forming events occurred, resulting in the presence of tubular and small shelly fossils. By simulating the growth environment of tubular fossils, we aim to improve our understanding of biotic turnover that took place during the end of the Ediacaran. In this study, we synthesised 'tubular fossils' with the same phosphorus content as modern seawater via electrochemical methods. The findings of this study provide a scientific basis for investigating the origin of the Cloudina tubular fossils and the reconstruction of the marine environment of the Ediacaran. [ABSTRACT FROM AUTHOR]

Foraminiferal wall micro/ultra-structures of Recent and well-preserved Jurassic (Bathonian) foraminifers of distinct foraminiferal high-rank taxonomic groups, Globothalamea (Rotaliida, Robertinida, and Textulariida), Miliolida, Spirillinata and Lagenata, are presented. Both calcite-cemented agglutinated and entirely calcareous foraminiferal walls have been investigated. Original test ultra-structures of Jurassic foraminifers are given for the first time. “Monocrystalline” wall-type which characterizes the class Spirillinata is documented in high resolution imaging. Globothalamea, Lagenata, porcelaneous representatives of Tubothalamea and Spirillinata display four different major types of wall-structure which may be related to distinct calcification processes. It confirms that these distinct molecular groups evolved separately, probably from single-chambered monothalamids, and independently developed unique wall types. Studied Jurassic simple bilocular taxa, characterized by undivided spiralling or irregular tubes, are composed of miliolid-type needle-shaped crystallites. In turn, spirillinid “monocrystalline” test structure has only been recorded within more complex, multilocular taxa possessing secondary subdivided chambers: Jurassic Paalzowella and Recent Patellina. More integrated molecular and structural studies are needed in order to better understand taxonomic position and phylogeny of tubular taxa. Unilocular and multichambered Lagenata (Lagenidae and Nodosariidae, respectively) show identical test micro and ultra-structure which suggests their close phylogenetic relationship and questions most recent theories of their separate evolutionary history and origins. A comparison of Recent, Cretaceous, and Jurassic foraminiferal test structure indicates that test characteristics at particular higher-rank taxonomic levels change very little over time and thus can serve as good proxies for the taxonomic designations of fossil taxa, when their state of preservation is appropriate for microstructural observations.

Spherical silica is a fundamentally important material with uses across a wide and diverse range of areas. However, the synthetic routes to producing spherical silica—typically Stöber processes—are inherently unsustainable and environmentally damaging. Petrochemical surfactants, alcoholic solvents, and ammonium hydroxide, which are commonly used, each have their own associated environmental problems. Demand is growing to find new, more sustainable ways, to synthesise spherical silica. Bioinspired and biomimetic silica, produced using knowledge learned from natural silica production methods such as biomineralisation, is an ever-growing field of research, that provides a possible route to more sustainable industrial silica production. Biomolecules can be used to shape and form spherical silica instead of petrochemical surfactants. Water-based chemistries can be used instead of alcohol solvents and ammonium hydroxide. This review establishes the parallels between the natural silica biomineralisation process and Stöber processes and focuses on the physicochemical properties necessary for biomolecules to synthesise spherical silica. Recent biomolecule-based syntheses are highlighted, and an outlook is given on further developments in the field. [ABSTRACT FROM AUTHOR]

Spherical silica particles are traditionally made via Stöber and modified-Stöber processes, which commonly use environmental toxins as reagents. Here we report a process to synthesise spherical silica particles using environmentally friendly biomolecules (phosphatidylcholine and soy lecithin) and employing water and soybean oil as solvents, rather than potentially harmful organic solvents. This scalable method represents an important step towards sustainable industrial silica syntheses. Under mildly acidic conditions phosphatidylcholine and soy lecithin can control the condensation of sodium silicate to form discrete, spherical silica particles. Silica particles with diameters ranging between 329 and 2232 nm were readily produced using phosphatidylcholine as the templating agent and soybean oil as the solvent in the presence of sodium silicate. Narrower size distributions (262–1272 nm) were achieved using soy lecithin as the templating agent in an aqueous acetate buffer solution containing sodium silicate. Silica particles grown using low concentrations of phosphatidylcholine and soy lecithin as templating agents formed by a combination of coalescence and Ostwald ripening, whilst particles grown at high concentrations predominantly formed through Ostwald ripening behaviour. The possibility of sustainably producing spherical silica particles in a simple biomolecule-templated synthesis is shown. [ABSTRACT FROM AUTHOR]

Whitlockite is a calcium phosphate that was first identified in minerals collected from the Palermo Quarry, New Hampshire. The terms magnesium whitlockite [Mg-whitlockite; Ca 18 Mg 2 (HPO 4) 2 (PO 4) 12 ] and beta-tricalcium phosphate [ β -TCP; β -Ca 3 (PO 4) 2 ] are often used interchangeably since Mg-whitlockite is not easily distinguished from β -Ca 3 (PO 4) 2 by powder X-ray diffraction although their crystalline structures differ significantly. Being both osteoconductive and bioresorbable, Mg-whitlockite is pursued as a synthetic bone graft substitute. In recent years, advances in development of synthetic Mg-whitlockite have been accompanied by claims that Mg-whitlockite is the second most abundant inorganic constituent of bone, occupying as much as 20–35 wt% of the inorganic fraction. To find evidence in support of this notion, this review presents an exhaustive summary of Mg-whitlockite identification in biological tissues. Mg-whitlockite is mainly found in association with pathological mineralisation of various soft tissues and dental calculus, and occasionally with enamel and dentine. With the exception of high-temperature treated tumoural calcified deposits around interphalangeal and metacarpal joints and rhomboidal Mg-whitlockite crystals in post-apoptotic osteocyte lacunae in human alveolar bone, this unusual mineral has never been detected in the extracellular matrix of mammalian bone. Characterisation techniques capable of unequivocally distinguishing between different calcium phosphate phases, such as high-resolution imaging, crystallography, and/or spectroscopy have exclusively identified bone mineral as poorly crystalline, ion-substituted, carbonated apatite. The idea that Mg-whitlockite is a significant constituent of bone mineral remains unsubstantiated. Contrary to claims that such biomaterials represent a bioinspired/biomimetic approach to bone repair, Mg-whitlockite remains, exclusively, a pathological biomineral. Magnesium whitlockite (Mg-whitlockite) is a unique calcium phosphate that typically features in pathological calcification of soft tissues; however, an alarming trend emerging in the synthetic bioceramics community claims that Mg-whitlockite occupies 20–35 wt% of bone mineral and therefore synthetic Mg-whitlockite represents a biomimetic approach towards bone regeneration. By providing an overview of Mg-whitlockite detection in biological tissues and scrutinising a diverse cross-section of literature relevant to bone composition analysis, this review concludes that Mg-whitlockite is exclusively a pathological biomineral, and having never been reported in bone extracellular matrix, Mg-whitlockite does not constitute a biomimetic strategy for bone repair. [Display omitted] [ABSTRACT FROM AUTHOR]

Spherical silica particles are typically made via Stöber processes. However, these processes are environmentally unsustainable. Here, we report a process to synthesise spherical silica particles in a more sustainable way using sodium caseinate. Initial experiments showed that sodium caseinate can replace the typical industrial structural directing agents used to produce spherical particles. Particles of 124 nm in size were produced with 200 mg L−1 sodium caseinate and 81 µL sodium silicate, and particles with a bimodal size distribution (258 and 1432 nm) were produced with 400 mg L−1 sodium caseinate and 81 µL sodium silicate. Particles with multimodal size distributions between 363–1588 nm and 342–860 nm where produced with 200 mg L−1 sodium caseinate and 162 µL sodium silicate and 200 mg L−1 sodium caseinate and 810 µL sodium silicate, respectively. Higher concentrations of sodium caseinate and low concentrations of sodium silicate promoted Ostwald ripening. Low concentrations of sodium caseinate and high concentrations of sodium silicate promoted coalescence. Subsequent optimisation of the monodispersity using a statistical design of experiments yielded size-monodisperse silica particles with a narrower size distribution between 172 and 340 nm using sodium caseinate, calcium chloride, sodium silicate, and acetate buffer. Analysis of variance (ANOVA) and regression analyses were used to determine and quantify the relationship between reagent concentrations and particle size. A regression equation was calculated, which predicts particle size based on reagent concentration. Predicted particle sizes (189.6, 197.1, 204.6, and 212.1 nm) and experimentally determined particle sizes (200, 190, 184, and 196 nm) showed good agreement. The possibility of producing spherical silica particles sustainably is shown. [ABSTRACT FROM AUTHOR]

Among the terrestrial Crustacea, isopods have most successfully established themselves in a large variety of terrestrial habitats. As in most Crustacea, their cuticle consists of a hierarchically organised organic phase of chitin-protein fibrils, containing calcium carbonate and some calcium phosphate. In previous studies, we examined the tergite cuticle of Tylos europaeus, which lives on seashores and burrows into moist sand. In this study, we investigate the closely related species Helleria brevicornis, which is completely terrestrial and lives in leaf litter and humus and burrows into the soil. To get deeper insights in relation between the structure of the organic and mineral phase in species living in diverse habitats, we have investigated the structure, and the chemical and crystallographic properties of the tergite cuticle using various preparation techniques, and microscopic and analytical methods. The results reveal long and short epicuticular sensilla with brushed tips on the tergite surface that do not occur in T. europaeus. As in T. europaeus a distal exocuticle, which contains a low number of organic fibres, contains calcite while the subjacent layers of the exo- and endocuticle contain amorphous calcium carbonate. The distal exocuticle contains a polygonal pattern of mineral initiation sites that correspond to interprismatic septa described for decapod crabs. The shape and position of calcite units do not follow the polygonal pattern of the septa. The results indicate that the calcite units form by crystallisation from an amorphous phase that progresses from both margins of the septa to the centres of the polygons.

Golden perch (Macquaria ambigua) is a freshwater game-fish native to central and southeast Australia. Larvae of this fish species were used in two different types of experiments to evaluate the effects of short-term exposures (up to 6 days) to aqueous gold, 5 nm gold nanoparticles (AuNPs), or 50 nm AuNPs. Relative to the control, increased gold concentrations corresponded with yolk-sac edema (swelling). Larvae exposed to 50 μM of 5 nm AuNPs had yolk-sacs that were ~1.5 times larger resulting in the appearance of bent notochords. After two days of exposure, 100% mortality was observed. Total mortalities were <25% in the other larvae–gold systems, suggesting that these larvae can quickly adapt to the presence of gold. In terms of an oxidative stress response, the larvae from all systems did not express high enzymatic activity. The state of the gold determined how much could be taken up (or immobilised) by a larva. Aqueous gold and 5 nm AuNPs easily pass through cells; therefore, larvae exposed to these forms of gold contained the highest concentrations. Scanning electron microscopy confirmed that cells comprising the epithelium and fins contained AuNPs. Aqueous gold was reduced to nanometre-scale particles within cells. Comparatively, 5 nm AuNPs appeared to be aggregated within cells forming clusters hundreds of nanometres in size. On the contrary, 50 nm AuNPs were not observed within cells but were detected within larvae by (single particle) inductively coupled plasma mass spectroscopy, suggesting that these AuNPs were probably taken up through the mouth or gills. The results of the present study demonstrate that exposure to AuNPs had adverse effects on developing golden perch larvae. Additionally, these effects were dependent on the size of the AuNPs. [ABSTRACT FROM AUTHOR]

Among bivalve muscles, the adductors are particularly important for animal survival because they control valve closure. Most studies have addressed the type and morphology of this muscle in bivalves but few have focused on the mechanism that anchors it to the shell myostracum layer. Moreover, the possible calcium transport mechanism through the adductor muscle cells to the myostracum shell layer, which is necessary for bivalve biomineralisation, has never been addressed. Our results indicate that the muscle cell-shell attachment is mediated by the outer mantle epithelial cell layer, here termed tendon cells. These cells are modified at the muscle scar zone by the presence of actin cytoskeletal bundles, which anchor cells to the extracellular matrix via focal adhesion (or focal contact) junctions at the basal side and to extrapallial matrix at the apical side, both rich in collagen. From apical focal adhesions, bundles of collagen-rich fibres cross the extrapallial space and penetrate the myostracum shell layer. The latter constitutes one of the strongest anchoring structures among invertebrates. Numerous vesicles protrude from the tendon cells into the extrapallial space. TEM-EDX analysis reveals the presence of Ca2+ inside some of these vesicles both in tendon cells and in the extrapallial space. This suggests a potential mechanism for calcium transport from cells to the myostracum. The interfaces between bivalve shells and muscular attachments are unique and of special interest as adhesive functional biomaterials, being one of the strongest invertebrate anchoring structures. We present an updated ultrastructural model of the adductor muscle-shell attachment. Muscle cells connect with the shell through epithelial 'tendon cells', which have a cytoskeleton of actin microfilaments that connect to the extracellular matrix via focal adhesions. Collagen-rich fibres arise from apical focal adhesions, cross the nanometric extrapallial space and penetrate the myostracum where they form an organic network. Calcium is present inside vesicles that are released into the extrapallial space. The lack of direct cellular control on secretion restricts the myostracal microstructure to prismatic aragonitic similar to its inorganic counterpart. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The aquatic bacterium Magnetospirillum gryphiswaldense synthesizes unique organelles. They consist of membrane-enveloped crystals of the iron mineral magnetite, and are used like a compass needle to align the cell along the Earth's magnetic field lines. Magnetotactic bacteria are a fascinating model-object to study biomineralization and microbial cell biology. Moreover, due to their remarkable properties they have recently attracted considerable interest as producers of magnetic nanoparticles for biotechnological and biomedical applications. [ABSTRACT FROM AUTHOR]

Obtaining rapid mineralisation is a challenge in current bone graft materials, which has been attributed to the difficulty of guiding the biological processes towards osteogenesis. Amelogenin, a key protein in enamel formation, inspired the design of two intrinsically disordered peptides (P2 and P6) that enhance in vivo bone formation, but the process is not fully understood. In this study, we have elucidated the mechanism by which these peptides induce improved mineralisation. Our molecular dynamics analysis demonstrated that in an aqueous environment, P2 and P6 fold to interact with the surrounding Ca 2+ , PO 4 3- and OH - ions, which can lead to apatite nucleation. Although P2 has a less stable backbone, it folds to a stable structure that allows for the nucleation of larger calcium phosphate aggregates than P6. These results were validated experimentally in a concentrated simulated body fluid solution, where the peptide solutions accelerated the mineralisation process compared to the control and yielded mineral structures mimicking the amorphous calcium phosphate crystals that can be found in lamella bone. A pH drop for the peptide groups suggests depletion of calcium and phosphate, a prerequisite for intrinsic osteoinduction, while S/TEM and SEM suggested that the peptide regulated the mineral nucleation into lamella flakes. Evidently, the peptides accelerate and guide mineral formation, elucidating the mechanism for how these peptides can improve the efficacy of P2 or P6 containing devices for bone regeneration. The work also demonstrates how experimental mineralisation study coupled with molecular dynamics is a valid method for understanding and predicting in vivo performance prior to animal trials., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The authors declare no financial and personal relationships with other people or organisations that could inappropriately influence bias to this work. IPR rights of the consensus peptides (US Patent US8367602B2 and connected titles) belong to Industrie Biomediche Insubri SA (Switzerland), where Giuseppe Perale is a founding shareholder and the executive vice president. The patent related to the consensus peptides was invented by Ståle Petter Lyngstadaas but has since been sold to Industrie Biomediche Insubri SA. NuPep AS, owned solely by Øystein Øvrebø, has a licencing right to the consensus peptides IPR above., (Published by Elsevier B.V.)

Phytoplankton play a central role in the regulation of global carbon and nutrient cycles, forming the basis of the marine food webs. A group of biogeochemically important phytoplankton, the coccolithophores, produce calcium carbonate scales that have been hypothesized to deter or reduce grazing by microzooplankton. Here, a meta-analysis of mesocosm-based experiments demonstrates that calcification of the cosmopolitan coccolithophore, Emiliania huxleyi, fails to deter microzooplankton grazing. The median grazing to growth ratio for E. huxleyi (0.56 ± 0.40) was not significantly different among non-calcified nano- or picoeukaryotes (0.71 ± 0.31 and 0.55 ± 0.34, respectively). Additionally, the environmental concentration of E. huxleyi did not drive preferential grazing of non-calcified groups. These results strongly suggest that the possession of coccoliths does not provide E. huxleyi effective protection from microzooplankton grazing. Such indiscriminate consumption has implications for the dissolution and fate of CaCO3 in the ocean, and the evolution of coccoliths.

Continual bone apposition at the cranial sutures provides the unique opportunity to understand how bone is built. Bone harvested from 16-week-old Sprague Dawley rat calvaria was either (i) deproteinised to isolate the inorganic phase (i.e., bone mineral) for secondary electron scanning electron microscopy or (ii) resin embedded for X-ray micro-computed tomography, backscattered electron scanning electron microscopy, and micro-Raman spectroscopy. Interdigitated finger-like projections form the interface between frontal and parietal bones. Viewed from the surface, bone mineral at the mineralisation front is comprised of nanoscale mineral platelets arranged into discrete, ~0.6–3.5 μm high and ~0.2–1.5 μm wide, marquise-shaped motifs that gradually evolve into a continuous interwoven mesh of mineralised bundles. Marquise-shaped motifs also contribute to the burial of osteoblastic–osteocytes by contributing to the roof over the lacunae. In cross-section, apices of the finger-like projections resemble islands of mineralised tissue, where new bone apposition at the surface is evident as low mineral density areas, while the marquise-shaped motifs appear as near-equiaxed assemblies of mineral platelets. Carbonated apatite content is higher towards the internal surface of the cranial vault. Up to 4 μm from the bone surface, strong Amide III, Pro, Hyp, and Phe signals, distinct PO43− bands, but negligible CO32– signal indicate recent bone formation and/or delayed maturation of the mineral. We show, for the first time, that the extracellular matrix of bone is assembled into micrometre-sized units, revealing a superstructure above the mineralised collagen fibril level, which has significant implications for function and mechanical competence of bone.

With ageing and pathological factors, dentine exposure becomes more and more commonplace in the clinic. The mechanical properties of dentine are far less than those of enamel. Once exposed, dentine exhibits a weak wear-resistance and then results in many oral diseases. Therefore, it is necessary to study effective measures to improve the wear-resistance of dentine. In this study, the effect of remineralisation on the mechanical properties and tribological behaviour of human dentine was studied in vitro using nano-indentation/scratch technique. Remineralisation treatment was conducted by immersing dentine specimens in casein phosphopeptides–amorphous calcium phosphate–asparagine-serine-serine solution for 7 days after 24 h pre-treatment in polydopamine solution. Results show that after the remineralisation treatment, dentine surface is covered with a layer of dense hydroxyapatite (HA) crystals with high crystallinity and preferential orientation, and dentinal tubules are occluded. Surface hardness and elastic modulus of dentine increase by 35 and 78%, respectively, and the wear volume decreases by 86%. The crystals that occlude the dentine tubules do not fall off on the worn surface. In sum, remineralisation enhances the mechanical properties and anti-wear performance of dentine surface by forming a hard covering consisting of dense HA crystals, which is a potential measure to prevent excessive tooth wear by dentine exposure.

ObjectiveA single Pro-70 to Thr (p.P70T) mutation of amelogenin is known to result in hypomineralised amelogenesis imperfecta (AI). This study aims to test the hypothesis that the given mutation affects the self-assembly of amelogenin molecules and impairs their ability to conduct the growth of apatite crystals.DesignRecombinant human full-length wild-type (rh174) and p.P70T mutated amelogenins were analysed using dynamic light scattering (DLS), protein quantification assay and atomic force microscopy (AFM) before and after the binding of amelogenins to hydroxyapatite crystals. The crystal growth modulated by both amelogenins in a dynamic titration system was observed using AFM.ResultsAs compared to rh174 amelogenin, p.P70T mutant displayed significantly increased sizes of the assemblies, higher binding affinity to apatite, and decreased crystal height.ConclusionPro-70 plays an important structural role in the biologically relevant amelogenin self-assembly. The disturbed regularity of amelogenin nanospheres by this single mutation resulted in an increased binding to apatite and inhibited crystal growth.

In an area named Mermian (municipality of Agde, South of France), a significant amount of fragmented italic amphorae from the 2nd century BC was discovered, located at a depth of 6 to 8 meters under the bed of the Hérault river. As no ship wreck was found in the vicinity, the reason of the presence of these amphora fragments, whose faces present a large accumulation of oyster shells, is unknown. Reconstructed geomorphological maps of the area present Mermian as a riverine site already at this period, and several hypothetical explanations on the role of these amphorae exist (landfill linked to a neighbouring habitat, bank reinforcement linked to a ford crossing, river landing, etc.). In order to define whether the amphorae were transported to this location and from where, we analysed the stable carbon and oxygen isotopes of the oyster shells. The δ13C and δ18O indicate that all oysters lived in the same environment, refuting a potential transport during the oyster accumulation. Moreover, the analysis of 'Mytilaster' sp. shells in the sediment around the oyster shells also reported a marine origin, suggesting that these oysters were also buried in a marine deposit. Transport to Mermian from a coastal locality is unlikely but may still have happened, although no trace of human handling were observed on the fragments. Still, the presence of other marine or brackish molluscs in the sediment discards the interpretation of Mermian being a continental locality.

Amorphous calcium carbonate (ACC) has been identified or inferred to exist in many groups of marine organisms that produce biominerals widely used as geochemical archives (e.g. foraminifera, molluscs, echinoderms). However, little is known about trace element incorporation into ACC, and thus it is not understood how precipitation through an ACC precursor might impact the fidelity of climate proxies and biomineralisation models built on the skeletal geochemistry of these marine calcifiers. To address this, we investigated the incorporation of Li, B, Na, Mg, Mn, Sr, Ba, and U into inorganic amorphous calcium magnesium carbonates precipitated from seawater under a variety of different carbonate chemistries, Mg/Ca ratios, and in the presence of aspartic and glutamic acid, two of the most common intracrystalline amino acids found in foraminifera and corals. ACC is highly enriched in most of these trace elements relative to the crystalline carbonates yet similar in some respects in terms of the factors influencing trace element partitioning. For example, ACC B/Ca is sensitive to the carbonate system, whilst Mg/Ca and Sr/Ca are largely a function of their respective ratio in seawater. In general, we find that most of the variance in the distribution coefficients of the other trace elements can be explained by some combination of the seawater carbonate chemistry and the seawater or ACC Mg/Ca ratio. [ABSTRACT FROM AUTHOR]

Summary: Carbon–calcium inclusions (CCaI) either as calcium oxalate crystals (CaOx) or amorphous calcium carbonate cystoliths are spread among most photosynthetic organisms. They represent dynamic structures with a significant construction cost and their appearance during evolution indicates an ancient origin. Both types of inclusions share some similar functional characteristics providing adaptive advantages such as the regulation of Ca levels, and the release of CO2 and water molecules upon decomposition. The latter seems to be essential under drought conditions and explains the intense occurrence of these structures in plants thriving in dry climates. It seems, however, that for plants CaOx may represent a more prevalent storage system compared with CaCO3 due to the multifunctionality of oxalate. This compound participates in a number of important soil biogeochemical processes, creates endosymbiosis with beneficial bacteria and provides tolerance against a combination of abiotic (nutrient deprivation, metal toxicity) and biotic (pathogens, herbivores) stress factors. We suggest a re‐evaluation of the roles of these fascinating plant structures under a new and holistic approach that could enhance our understanding of carbon sequestration at the whole plant level and provide future perspectives. [ABSTRACT FROM AUTHOR]

With ageing and pathological factors, dentine exposure becomes more and more commonplace in the clinic. The mechanical properties of dentine are far less than those of enamel. Once exposed, dentine exhibits a weak wear‐resistance and then results in many oral diseases. Therefore, it is necessary to study effective measures to improve the wear‐resistance of dentine. In this study, the effect of remineralisation on the mechanical properties and tribological behaviour of human dentine was studied in vitro using nano‐indentation/scratch technique. Remineralisation treatment was conducted by immersing dentine specimens in casein phosphopeptides–amorphous calcium phosphate–asparagine‐serine‐serine solution for 7 days after 24 h pre‐treatment in polydopamine solution. Results show that after the remineralisation treatment, dentine surface is covered with a layer of dense hydroxyapatite (HA) crystals with high crystallinity and preferential orientation, and dentinal tubules are occluded. Surface hardness and elastic modulus of dentine increase by 35 and 78%, respectively, and the wear volume decreases by 86%. The crystals that occlude the dentine tubules do not fall off on the worn surface. In sum, remineralisation enhances the mechanical properties and anti‐wear performance of dentine surface by forming a hard covering consisting of dense HA crystals, which is a potential measure to prevent excessive tooth wear by dentine exposure. [ABSTRACT FROM AUTHOR]

Molar hypomineralisation (MH) is becoming globally recognised as a significant public health problem linked to childhood tooth decay. However, with causation and pathogenesis unclear after 100 years of investigation, better pathological understanding is needed if MH is to become preventable. Our studies have implicated serum albumin in an extracellular pathomechanism for chalky enamel, opposing longheld dogma about systemic injury to enamel-forming cells. Hypothesising that chalky enamel arises through developmental exposure to serum albumin, this study used biochemical approaches to characterise demarcated opacities from 6-year molars. Addressing contradictory literature, normal enamel was found to completely lack albumin subject to removal of surface contamination. Querying surface permeability, intact opacities were found to lack salivary amylase, indicating that "enamel albumin" had become entrapped before tooth eruption. Thirdly, comparative profiling of chalky and hard-white enamel supported a dose-response relationship between albumin and clinical hardness of opacities. Moreover, albumin abundance delineated chalky enamel from white transitional enamel at opacity borders. Finally, addressing the corollary that enamel albumin had been entrapped for several years, clear signs of molecular ageing (oxidative aggregation and fragmentation) were identified. By establishing aged albumin as a biomarker for chalky enamel, these findings hold methodological, clinical, and aetiological significance. Foremost, direct inhibition of enamel-crystal growth by albumin (here termed "mineralisation poisoning") at last provides a cogent explanation for the clinical presentation of demarcated opacities. Together, these findings justify pursuit of an extracellular paradigm for the pathogenesis of MH and offer exciting new prospects for alleviating childhood tooth decay through medical prevention of MH. [ABSTRACT FROM AUTHOR]

Molar Hypomineralisation (MH) is gaining cross-sector attention as a global health problem, making deeper enquiry into its prevention a research priority. However, causation and pathogenesis of MH remain unclear despite 100 years of investigation into "chalky" dental enamel. Contradicting aetiological dogma involving disrupted enamel-forming cells (ameloblasts), our earlier biochemical analysis of chalky enamel opacities implicated extracellular serum albumin in enamel hypomineralisation. This study sought evidence that the albumin found in chalky enamel reflected causal events during enamel development rather than later association with pre-existing enamel porosity. Hypothesising that blood-derived albumin infiltrates immature enamel and directly blocks its hardening, we developed a "molecular timestamping" method that quantifies the adult and fetal isoforms of serum albumin ratiometrically. Applying this novel approach to 6-year molars, both isoforms of albumin were detectable in 6 of 8 chalky opacities examined (corresponding to 4 of 5 cases), indicating developmental acquisition during early infancy. Addressing protein survival, in vitro analysis showed that, like adult albumin, the fetal isoform (alpha-fetoprotein) bound hydroxyapatite avidly and was resistant to kallikrein-4, the pivotal protease involved in enamel hardening. These results shift primary attention from ameloblast injury and indicate instead that an extracellular mechanism involving localised exposure of immature enamel to serum albumin constitutes the crux of MH pathogenesis. Together, our pathomechanistic findings plus the biomarker approach for onset timing open a new direction for aetiological investigations into the medical prevention of MH. [ABSTRACT FROM AUTHOR]

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Highly ordered superstructures composed of inorganic nanoparticles appear in natural and synthetic systems, however the mechanisms of non‐equilibrium self‐organization that may be involved are still poorly understood. Herein, we performed a kinetic investigation of the precipitation of calcium phosphate using a process widely found in microorganisms: the hydrolysis of urea by enzyme urease. With high initial ratio of calcium ion to phosphate, periodic precipitation was obtained accompanied by pH oscillations in a well‐stirred, closed reactor. We propose that an internal pH‐regulated change in the concentration of phosphate ion is the driving force for periodicity. A simple model involving the biocatalytic reaction network coupled with burst nucleation of nanoparticles above a critical supersaturation reproduced key features of the experiments. These findings may provide insight to the self‐organization of nanoparticles in biomineralization and improve design strategies of biomaterials for medical applications. [ABSTRACT FROM AUTHOR]

In an area named Mermian (municipality of Agde, South of France), a significant amount of fragmented italic amphorae from the 2nd century BC was discovered, located at a depth of 6 to 8 meters under the bed of the Hérault river. As no ship wreck was found in the vicinity, the reason of the presence of these amphora fragments, whose faces present a large accumulation of oyster shells, is unknown. Reconstructed geomorphological maps of the area present Mermian as a riverine site already at this period, and several hypothetical explanations on the role of these amphorae exist (landfill linked to a neighbouring habitat, bank reinforcement linked to a ford crossing, river landing, etc.). In order to define whether the amphorae were transported to this location and from where, we analysed the stable carbon and oxygen isotopes of the oyster shells. The d13C and d18O indicate that all oysters lived in the same environment, refuting a potential transport during the oyster accumulation. Moreover, the analysis of Mytilaster sp. shells in the sediment around the oyster shells also reported a marine origin, suggesting that these oysters were also buried in a marine deposit. Transport to Mermian from a coastal locality is unlikely but may still have happened, although no trace of human handling were observed on the fragments. Still, the presence of other marine or brackish molluscs in the sediment discards the interpretation of Mermian being a continental locality. [ABSTRACT FROM AUTHOR]

A significant surge in the exploitation of uranium resources has resulted in considerable amounts of radioactive effluents. Thus, efficient and eco-friendly uranium removal strategies need to be explored to ensure ecological safety and resource recovery. In this study, we investigated the resistance of Halomonas campaniensis strain ZFSY-04, isolated from an evaporation pool at a uranium mine site, and its potential mechanism of uranium (Ⅵ) removal. The results showed that the strain exhibited unique uranium tolerance and its growth was not significantly inhibited under a uranium concentration of 700 mg/L. It had a maximum loading capacity of 865.40 mg/g (dry weight), achieved following incubation under uranium concentration of 100 mg/L, pH 6.0, and temperature 30 °C, for 2 h, indicating that the removal of uranium by the strain was efficient and rapid. Combined with kinetic, isothermal, thermodynamic, and microspectral analyses, the mechanism of uranium loading by strain ZFSY-04 was metabolism-dependent and diverse, including, physical and chemical adsorption on the cell surface, extracellular biomineralisation, intracellular bioaccumulation, and biomineralisation. Our results highlight the unique properties of indigenous strains, including high resistance, high efficiency, rapid uranium removal, and various uranium removal strategies, which make it suitable as a new tool for in situ bioremediation and uranium-contaminated environmental resource recovery. [Display omitted] • ZFSY-04 exhibits unique uranium tolerance because of isolating from an evaporation pool of ISL uranium mine. • ZFSY-04 has the immense potential for rapid and efficient uranium removal. • The mechanism of uranium loading by ZFSY-04 is metabolism-dependent and diverse. • ZFSY-04 is suitable as a new tool for in situ bioremediation and uranium-contaminated environmental resource recovery. [ABSTRACT FROM AUTHOR]

The sulphate-reducing bacteria (SRB) of genus Desulfovibrio are a group of prokaryotes associated with autism spectrum disorders (ASD). The connection between the elevated numbers of Desulfovibrio in the gut of children with ASD compared with healthy children remains unresolved. A conceivable consequence of SRB overgrowth in the gut is the conversion of bioavailable iron into low-soluble crystalline iron sulphides, causing iron deficiency in the organism. In this study, we report the draft genome sequence and physiological features of the first cultivable isolate from a patient with ASD, Desulfovibrio desulfuricans strain AY5.The capability of the strain to produce crystalline iron sulphides was studied under different pH conditions. The most notable greigite(Fe3S4) and pyrite (FeS2) formation was revealed at pH 6.0, which suggests that the iron loss due to insoluble sulphide formation may occur in the proximal part of the gastrointestinal tract. Strain AY5 was adapted to grow under nitrogen-limiting conditions by N2 fixation. The urease found in the strain’s genome may play a role in resistance to acidic pH.

Inorganic systems based upon polyoxometalate (POM) clusters provide an experimental approach to develop artificial life. These artificial symmetric anionic macromolecules with oxidometalate polyhedra as building blocks were shown to be well suited as inorganic frameworks for complex self-assembling and organizing systems with emergent properties. Analogously to mineral cells based on iron sulfides, POMs are considered as inorganic cells in facilitating prelife chemical processes and displaying “life-like” characteristics. However, the relevance of POMs to life-sustaining processes (e.g., microbial respiration) has not yet been addressed, while iron sulfides are very well known as ubiquitous mineral precursors and energy sources for chemolithotrophic metabolism. Metallosphaera sedula is an extreme metallophilic and thermoacidophilic archaeon, which flourishes in hot acid and respires by metal oxidation. In the present study we provide our observations on M. sedula cultivated on tungsten polyoxometalate (W-POM). The decomposition of W-POM macromolecular clusters and the appearance of low molecular weight W species (e.g., WO) in the presence of M. sedula have been detected by electrospray ionization mass spectrometry (ESI-MS) analysis. Here, we document the presence of metalloorganic assemblages at the interface between M. sedula and W-POM resolved down to the nanometer scale using scanning and transmission electron microscopy (SEM and TEM) coupled to electron energy loss spectroscopy (EELS). High-resolution TEM (HR-TEM) and selected-area electron diffraction (SAED) patterns indicated the deposition of redox heterogeneous tungsten species on the S-layer of M. sedula along with the accumulation of intracellular tungsten-bearing nanoparticles, i.e., clusters of tungsten atoms. These results reveal the effectiveness of the analytical spectroscopy coupled to the wet chemistry approach as a tool in the analysis of metal–microbial interactions and microbial cultivation on supramolecular self-assemblages based on inorganic metal clusters. We discuss the possible mechanism of W-POM decomposition by M. sedula in light of unique electrochemical properties of POMs. The findings presented herein highlight unique metallophilicity in hostile environments, extending our knowledge of the relevance of POMs to life-sustaining processes, understanding of the transition of POMs as inorganic prebiotic model to life-sustainable material precursors and revealing biogenic signatures obtained after the decomposition of an artificial inorganic compound, which previously was not associated with any living matter.

Gold and platinum-group-metals (PGM) are cycled through Earth's environments by interwoven geological, physical, chemical and biological processes leading to the trans/neoformation of metallic particles in placers. The placer deposit at Corrego Bom Successo (CBS, Brazil) is one of the few localities worldwide containing secondary gold- and PGM-particles. Placer gold consists of detrital particles from nearby hydrothermal deposits that were transformed in the surface environment. Processes that have affected these particles include short-distance transport, chemical de-alloying of the primary gold‑silver, and (bio)geochemical dissolution/re-precipitation of gold leading to the formation of pure, secondary gold and the dispersion of gold nanoparticles. The latter processes are likely mediated by non-living organic matter (OM) and bacterial biofilms residing on the particles. The biofilms are largely composed of metallophillic β- and γ-Proteobacteria. Abundant mobile gold and platinum nanoparticles were detected in surface waters, suggesting similar mobilities of these metals. Earlier hydrothermal processes have led to the formation of coarsely-crystalline, arborescent dendritic potarite (PdHg). On potarite surfaces, biogeochemical processes have then led to the formation of platinum- and palladium-rich micro-crystalline layers, which make up the botryoidal platinum‑palladium aggregates. Subsequently potarite was dissolved from the core of many aggregates leaving voids now often filled by secondary anatase (TiO 2) containing biophilic elements. The presence of fungal structures associated with the anatase suggests that fungi may have contributed to its formation. For the first time a primary magmatic PGM-particle comprising a mono-crystalline platinum‑palladium-alloy with platinum‑iridium‑osmium inclusions was described from this locality, finally defining a possible primary source for the PGM mineralisation. In conclusion, the formation of modern-day placer gold- and PGM-particles at CBS began 100s of millions of years ago by magmatic and hydrothermal processes. These provided the metal sources for more recent biogeochemical cycling of PGEs and gold that led to the trans/neoformation of gold- and PGM-particles. Unlabelled Image • Gold and platinum-group-elements are subject to biogeochemical cycling in the placer environment. • Mobilisation and re-precipitation in (paleo)-placers drives gold and platinum-group-metal (PGM) particles (trans)formation. • Microbial biofilms capable of mediating these processes are present on gold and PGM particles. • Mobile mercury results in mercury toxicity that may drive a fast biological cycling of platinum and palladium. • Modern-day gold and PGM particles placer began 100s of millions of years ago by magmatic and hydrothermal processes. [ABSTRACT FROM AUTHOR]

The consolidation of soft limestones has since long been practiced by using various products applied by different procedures, both for laboratory conditions and as real conservation actions. However, the actual performances of these consolidants have always left doubts, mostly as regards to their long-term – and, in some situations, short-term – behaviour when used for outdoor objects. The encouraging results that have been reported for the biomineralisation process in limestones, both for laboratory conditions and in trial tests, led to test it under onsite conditions to assess the operational aspects, as well as on a conservation intervention carried out for a limestone portal in the south of Portugal. The biotechnology approach reported here resorts to the activation of carbonatogenic bacteria present in the substrate's microbiota. In this paper, the main steps and logistics requirements for this consolidation treatment - environmental control, product transport and application conditions – are summarised, onsite test results are presented and discussed, and its application in a conservation intervention is described and commented. The onset of this new consolidation treatment led us to revisit past experiences on Portuguese heritage objects as an opportunity to discuss the practical significance and applicability of the concepts of effectiveness and compatibility in the consolidation of soft calcareous stone materials. A new conceptual and practical approach to deal with the very complex and difficult problem posed by the consolidation of real outdoor exposed and decayed objects is proposed. The discussion is based on the authors' experience on four Portuguese monuments: the Santa Cruz church (Coimbra), the Porta Especiosa of the Old Cathedral of Coimbra, the National Palace of Queluz, and the Main Portal of the Loulé church. The potential of the method and its encouraging results may represent the crossing of a new technological and practical frontier to consolidate decayed highly porous limestones. [ABSTRACT FROM AUTHOR]

Inorganic systems based upon polyoxometalate (POM) clusters provide an experimental approach to develop artificial life. These artificial symmetric anionic macromolecules with oxidometalate polyhedra as building blocks were shown to be well suited as inorganic frameworks for complex self-assembling and organizing systems with emergent properties. Analogously to mineral cells based on iron sulfides, POMs are considered as inorganic cells in facilitating prelife chemical processes and displaying "life-like" characteristics. However, the relevance of POMs to life-sustaining processes (e.g., microbial respiration) has not yet been addressed, while iron sulfides are very well known as ubiquitous mineral precursors and energy sources for chemolithotrophic metabolism. Metallosphaera sedula is an extreme metallophilic and thermoacidophilic archaeon, which flourishes in hot acid and respires by metal oxidation. In the present study we provide our observations on M. sedula cultivated on tungsten polyoxometalate (W-POM). The decomposition of W-POM macromolecular clusters and the appearance of low molecular weight W species (e.g., WO) in the presence of M. sedula have been detected by electrospray ionization mass spectrometry (ESI-MS) analysis. Here, we document the presence of metalloorganic assemblages at the interface between M. sedula and W-POM resolved down to the nanometer scale using scanning and transmission electron microscopy (SEM and TEM) coupled to electron energy loss spectroscopy (EELS). High-resolution TEM (HR-TEM) and selected-area electron diffraction (SAED) patterns indicated the deposition of redox heterogeneous tungsten species on the S-layer of M. sedula along with the accumulation of intracellular tungsten-bearing nanoparticles, i.e., clusters of tungsten atoms. These results reveal the effectiveness of the analytical spectroscopy coupled to the wet chemistry approach as a tool in the analysis of metal–microbial interactions and microbial cultivation on supramolecular self-assemblages based on inorganic metal clusters. We discuss the possible mechanism of W-POM decomposition by M. sedula in light of unique electrochemical properties of POMs. The findings presented herein highlight unique metallophilicity in hostile environments, extending our knowledge of the relevance of POMs to life-sustaining processes, understanding of the transition of POMs as inorganic prebiotic model to life-sustainable material precursors and revealing biogenic signatures obtained after the decomposition of an artificial inorganic compound, which previously was not associated with any living matter. [ABSTRACT FROM AUTHOR]

High-latitude cold-water coral reefs are particularly vulnerable to climate change due to enhanced CO 2 uptake in these regions. To evaluate their physiological functioning and potential application as pH archives, we retrieved both recent and fossil samples of Lophelia pertusa along the Norwegian margin from Oslofjord (59°N), over to Trondheimsfjord, Sula and Lopphavet (70.6°N). Boron isotope analyses (δ11B) were undertaken using solution-based and laser ablation multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS; LA-ICP-MS), and secondary ion mass spectrometry (SIMS). Epi-fluorescence microscopy was employed to provide a rapid pre-screening routine for structure-specific subsampling in the coral skeleton. This integrated approach enabled us to assess heterogeneities within single specimens, as well as to investigate the role of local environmental influences including recent and past variations. All three mass spectrometry methods show substantial differences in the δ11B of the theca wall (TW) and the centres of calcification (COC's). Micro-bulk subsamples milled from the theca wall of modern specimens originating from different habitats but with comparable seawater pH (8–8.16) gave consistent δ11B values averaging 26.7 (±0.2‰, 2σ, n = 4), while COC subsamples systematically deviated towards lower B/Ca (by ~40%) and depleted δ11B values (minimum 22.7 ± 0.3‰, 2σ), implying a difference of at least 4‰ between TW and COC. SIMS and LA-ICP-MS measurements identified much larger internal heterogeneities with maximum variation of ~10‰ between the distinct skeletal structures; minimal SIMS δ11B values of ~17.3 ± 1.2‰ (2σ) were associated with the pure COC material. Our findings may be interpreted in terms of the occurrence of two main, but likely different, biomineralisation mechanisms in L. pertusa , with the COC's generally exhibiting minimal pH up-regulation, potentially supporting the use of bicarbonate in the early stages of biomineralisation. Furthermore, we highlight the potential utility of L. pertusa for palaeo-proxy studies if targeting the compositionally homogenous TW zones devoid of COC admixtures, which appear to provide highly reproducible measurements. [ABSTRACT FROM AUTHOR]

Abstract We studied Mg/Ca, Sr/Ca and Ca isotope ratios of ostracod carapaxes from surface sediments retrieved during research cruises to the Southern and Equatorial Eastern Atlantic. Collected specimens originate from water depth between 30 and about 5000 mbsl and cover bottom water temperatures between 0 and 23 °C. Analysed taxa include Buntonia sp., Cytherella sp., Henryhowella sp., Krithe sp., Poseidonamicus sp., and Ruggieria sp. Calcium isotope ratios of the studied specimens are in the overall range of other marine calcifiers and show a variability of about 0.75‰ over a temperature range of ~20 °C. There is no overall linear relation between temperature and Ca isotope fractionation, but some species show a maximum δ44/40Ca at intermediate temperatures. Mg/Ca and Sr/Ca agree well with values of previously published carapaxes, demonstrating large inter- and intra-species variability and different responses to bottom water temperatures. Magnesium is highly variably distributed within the carapax, with Mg enrichment in the inner part of the shell of most taxa. This enrichment is independent from the incorporation of Sr, which shows less variability within the carapax. The Ca isotope vs. Sr/Ca systematic in the ostracods deviates from inorganic calcite and foraminifers. The ostracod array is most likely controlled by either mixing of material originating from a precursor phase and newly grown calcite or Rayleigh type fractionation during precipitation from a restricted fluid reservoir, indicating varying degrees of Ca and Sr consumption during calcite precipitation. The different slope of the Ca isotope vs. Sr/Ca relation shown by the ostracods compared to those of inorganic calcite and foraminifers opens a new approach for the determination of Ca isotope and Sr/Ca ratios of past ocean water. Highlights • Ostracods show inter- and intra-species variability in δ44/40Ca. • Ca isotopes are apparently not directly controlled by environmental factors. • Ostracods follow special δ44/40Ca and Sr/Ca fractionation array. [ABSTRACT FROM AUTHOR]

Abstract Groundwater at legacy nuclear facilities around the world is contaminated with radionuclides including strontium-90 and technetium-99, which are often present as co-contaminants. Here we investigated whether biostimulation of indigenous microbial communities by glycerol phosphate can co-treat 90Sr through incorporation into phosphate biominerals, and 99Tc through microbially-induced reduction of the sediment to form less mobile Tc(IV) phases via reaction with reduced species (e.g. Fe(II)). Results showed that 95% of Sr was removed from solution in sediment microcosms treated with glycerol phosphate, and sequential extraction showed that ~18% of the Sr in the resulting solid phase was associated with the pH 5 Na-acetate fraction and 75% was in the ion exchangeable fraction. This removal and partitioning to recalcitrant phases during glycerol phosphate treatment was greater than in the untreated controls, where only 60% of Sr was removed from solution, and of the solid-associated Sr, 95% was present in the exchangeable fraction. Fitting of Sr K -edge EXAFS spectra confirmed these findings, with shell by shell fitting suggesting ~30% of sediment-associated Sr was present in a coordination environment consistent with phosphate biominerals following glycerol phosphate treatment, whilst Sr was present only as outer-sphere complexes in the controls. In addition,16S rRNA sequencing of sediments stimulated with glycerol phosphate demonstrated the growth of potential phosphate-solubilising species such as Chryseobacterium and Serratia spp. Finally, glycerol phosphate treatment stimulated bioreduction via addition of electron donor in the form of glycerol to the system, in turn this stimulated the removal of 99Tc from solution concomitant with microbial Fe(III) reduction to form poorly soluble hydrous Tc(IV)O 2 like phases. In sediments amended with an electron donor, the microbial community also reflected the onset of bioreduction with an increased relative abundance of Fe(III) and sulfate-reducing bacteria such as Geothrix , Geobacter and Desulfobulbus spp. Overall these results suggest application of glycerol phosphate offers a promising bioremediation strategy to co-treat both 90Sr and 99Tc contaminated groundwaters, and promotes the formation of Sr-phosphate and Tc(IV) bearing biominerals when reducing conditions are maintained. Combined with past work which shows the scavenging of uranium from solution following addition of glycerol phosphate, this extends the scope for glycerol phosphate as a treatment for radioactive contamination in groundwaters. [ABSTRACT FROM AUTHOR]

Abstract CO 2 -induced ocean acidification and associated decrease of seawater carbonate saturation state contributed to multiple environmental crises in Earth's history, and currently poses a major threat for marine calcifying organisms. Owing to their high abundance and good preservation in the Phanerozoic geological record, brachiopods present an advantageous taxon of marine calcifiers for palaeo-proxy applications as well as studies on biological mechanism to cope with environmental change. To investigate the geochemical and physiological responses of brachiopods to prolonged low-pH conditions we cultured Magellania venosa , Terebratella dorsata and Pajaudina atlantica under controlled experimental settings over a period of more than two years. Our experiments demonstrate that brachiopods form their calcite shells under strong biological control, which enables them to survive and grow under low-pH conditions and even in seawater strongly undersaturated with respect to calcite (pH = 7.35, Ω cal = 0.6). Using boron isotope (δ11B) systematics including MC-ICP-MS as well as SIMS analyses, validated against in vivo microelectrode measurements, we show that this resilience is achieved by strict regulation of the calcifying fluid pH between the epithelial mantle and the shell. We provide a culture-based δ11B−pH calibration, which as a result of the internal pH regulatory mechanisms deviates from the inorganic borate ion to pH relationship, but confirms a clear yet subtle pH dependency for brachiopods. At a micro-scale level, the incorporation of boron appears to be principally driven by a physiological gradient across the shell, where the δ11B values of the innermost calcite record the internal calcifying fluid pH while the composition of the outermost layers is also influenced by seawater pH. These findings are of consequence to studies on biomineralisation processes, physiological adaptations as well as past climate reconstructions. [ABSTRACT FROM AUTHOR]

Abstract Assessing the physicochemical variability of the deeper ocean is currently hampered by limited instrumental time series and proxy records. Bamboo corals (Isididae) form a cosmopolitan family of calcitic deep sea corals that could fill this information gap via geochemical information recorded in their skeletons. Here we evaluate the suitability of high-resolution chemical imaging of bamboo coral skeletons for temperature and nutrient reconstruction. The applied elemental mapping techniques allow to verify the suitability of the chosen transect on the sample section for paleo-reconstructions and enhance the statistical precision of the reconstruction. We measured Mg/Ca via electron microprobe at 1 μm resolution and Ba/Ca via laser ablation ICP-MS at 35 μm resolution in a historic specimen of Keratoisis grayi from the Blake Plateau off Eastern Florida. Long-term growth temperatures of 7.1 ± 3.4 °C (2SD) that are in agreement with recent ambient temperature range can be reconstructed from Mg/Ca ratios provided that anomalously Mg-enriched structural features around the central axis and isolated features related to tissue attachment are avoided for reconstruction. Skeletal Ba/Ca measurements reflect mean seawater barium [Ba] SW concentrations ([Ba] SW = 51 ± 24 nmol kg−1 (2SD)), in agreement with instrumental data (47 nmol kg−1). We show for the first time that Ba/Ca forms concentric structures in a bamboo coral skeleton section. Our investigations suggest that, while bamboo coral skeletons do record environmental parameters in their mean chemical composition, the magnitude of environmental variability reconstructed from high-resolution chemical maps exceeds that expected from instrumental time series. This necessitates additional investigation of the factors driving bamboo coral skeletal composition. [ABSTRACT FROM AUTHOR]

Foraminiferal wall micro/ultra-structures of Recent and well-preserved Jurassic (Bathonian) foraminifers of distinct foraminiferal high-rank taxonomic groups, Globothalamea (Rotaliida, Robertinida, and Textulariida), Miliolida, Spirillinata and Lagenata, are presented. Both calcite-cemented agglutinated and entirely calcareous foraminiferal walls have been investigated. Original test ultra-structures of Jurassic foraminifers are given for the first time. "Monocrystalline" wall-type which characterizes the class Spirillinata is documented in high resolution imaging. Globothalamea, Lagenata, porcelaneous representatives of Tubothalamea and Spirillinata display four different major types of wall-structure which may be related to distinct calcification processes. It confirms that these distinct molecular groups evolved separately, probably from single-chambered monothalamids, and independently developed unique wall types. Studied Jurassic simple bilocular taxa, characterized by undivided spiralling or irregular tubes, are composed of miliolid-type needle-shaped crystallites. In turn, spirillinid "monocrystalline" test structure has only been recorded within more complex, multilocular taxa possessing secondary subdivided chambers: Jurassic Paalzowella and Recent Patellina. More integrated molecular and structural studies are needed in order to better understand taxonomic position and phylogeny of tubular taxa. Unilocular and multichambered Lagenata (Lagenidae and Nodosariidae, respectively) show identical test micro and ultra-structure which suggests their close phylogenetic relationship and questions most recent theories of their separate evolutionary history and origins. A comparison of Recent, Cretaceous, and Jurassic foraminiferal test structure indicates that test characteristics at particular higher-rank taxonomic levels change very little over time and thus can serve as good proxies for the taxonomic designations of fossil taxa, when their state of preservation is appropriate for microstructural observations. [ABSTRACT FROM AUTHOR]