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Ehrlich, Hermann, Elizabeth Bailey, Marcin Wysokowski y Teofil Jesionowski. "Forced Biomineralization: A Review". Biomimetics 6, n.º 3 (12 de julio de 2021): 46. http://dx.doi.org/10.3390/biomimetics6030046.
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Biologically induced and controlled mineralization of metals promotes the development of protective structures to shield cells from thermal, chemical, and ultraviolet stresses. Metal biomineralization is widely considered to have been relevant for the survival of life in the environmental conditions of ancient terrestrial oceans. Similar behavior is seen among extremophilic biomineralizers today, which have evolved to inhabit a variety of industrial aqueous environments with elevated metal concentrations. As an example of extreme biomineralization, we introduce the category of “forced biomineralization”, which we use to refer to the biologically mediated sequestration of dissolved metals and metalloids into minerals. We discuss forced mineralization as it is known to be carried out by a variety of organisms, including polyextremophiles in a range of psychrophilic, thermophilic, anaerobic, alkaliphilic, acidophilic, and halophilic conditions, as well as in environments with very high or toxic metal ion concentrations. While much additional work lies ahead to characterize the various pathways by which these biominerals form, forced biomineralization has been shown to provide insights for the progression of extreme biomimetics, allowing for promising new forays into creating the next generation of composites using organic-templating approaches under biologically extreme laboratory conditions relevant to a wide range of industrial conditions.
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Pamirsky, Igor E. y Kirill S. Golokhvast. "Origin and Status of Homologous Proteins of Biomineralization (Biosilicification) in the Taxonomy of Phylogenetic Domains". BioMed Research International 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/397278.
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The taxonomic affiliation (in the systematisation of viruses, and biological domains) of known peptides and proteins of biomineralization (silicateins, silaffins, silacidins and silicase) and their primary structure homologues were analyzed (methodsin silico; using Uniprot database). The total number of known peptides and proteins of biosilicification was counted. The data of the quantitative distribution of the detected homologues found in nature are presented. The similarity of the primary structures of silaffins, silacidins, silicateins, silicase, and their homologues was 21–94%, 45–98%, 39–50%, and 28–40%, respectively. These homologues are found in many organisms, from the Protista to the higher plants and animals, including humans, as well as in bacteria and extracellular agents, and they perform a variety of biological functions, such as biologically controlled mineralisation. The provisional classification of these biomineralization proteins is presented. The interrelation of the origin of the first organic polymers and biomineralization is discussed.
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Okada, Satoshi, Chong Chen, Tomo-o. Watsuji, Manabu Nishizawa, Yohey Suzuki, Yuji Sano, Dass Bissessur, Shigeru Deguchi y Ken Takai. "The making of natural iron sulfide nanoparticles in a hot vent snail". Proceedings of the National Academy of Sciences 116, n.º 41 (24 de septiembre de 2019): 20376–81. http://dx.doi.org/10.1073/pnas.1908533116.
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Biomineralization in animals exclusively features oxygen-based minerals with a single exception of the scaly-foot gastropod Chrysomallon squamiferum, the only metazoan with an iron sulfide skeleton. This unique snail inhabits deep-sea hot vents and possesses scales infused with iron sulfide nanoparticles, including pyrite, giving it a characteristic metallic black sheen. Since the scaly-foot is capable of making iron sulfide nanoparticles in its natural habitat at a relatively low temperature (∼15 °C) and in a chemically dynamic vent environment, elucidating its biomineralization pathways is expected to have significant industrial applications for the production of metal chalcogenide nanoparticles. Nevertheless, this biomineralization has remained a mystery for decades since the snail’s discovery, except that it requires the environment to be rich in iron, with a white population lacking in iron sulfide known from a naturally iron-poor locality. Here, we reveal a biologically controlled mineralization mechanism employed by the scaly-foot snail to achieve this nanoparticle biomineralization, through δ34 S measurements and detailed electron-microscopic investigations of both natural scales and scales from the white population artificially incubated in an iron-rich environment. We show that the scaly-foot snail mediates biomineralization in its scales by supplying sulfur through channel-like columns in which reaction with iron ions diffusing inward from the surrounding vent fluid mineralizes iron sulfides.
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SAKURAI, S., R. ASAKAWA, F. HIROTA, T. SATO, K. SERA y J. ITOH. "QUANTITATIVE AND QUALITATIVE ANALYSIS OF FLUORIDE AND MULTI ELEMENTS OF SHARK TEETH BY PIXE". International Journal of PIXE 18, n.º 03n04 (enero de 2008): 123–29. http://dx.doi.org/10.1142/s0129083508001466.
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Biomineralization has two types, biologically induced mineralization (BIM) and biologically controlled mineralization (BCM). Shark teeth is a typical representative of BCM. We have measured concentrations of fluorine and multi elements in shark teeth collected in the south of Japan. As a result, it was confirmed that the sample preparation method, which was established for the biological samples, is applicable to the shark teeth samples and the elemental concentration was obtained in good accuracy and reproducibility. Moreover, we clarified that the shark teeth is composed of Fluorapatite by the combination with X-ray Diffraction. Fluorine concentration is found to be 5500 µg/g in the shark teeth. We have 100 samples of Shark teeth and are planning on reporting the findings of a study with larger samples in the near future.
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Cuéllar-Cruz, Mayra, Karina Sandra Pérez, María Eugenia Mendoza y Abel Moreno. "Biocrystals in Plants: A Short Review on Biomineralization Processes and the Role of Phototropins into the Uptake of Calcium". Crystals 10, n.º 7 (9 de julio de 2020): 591. http://dx.doi.org/10.3390/cryst10070591.
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The biomineralization process is a mechanism inherent to all organisms of the Earth. Throughout the decades, diverse works have reported that the origin of life is tied to crystals, specifically to biominerals of silica that catalyzed RNA, and had some influence in the homochirality. Although the mechanism by which crystals surfaces (minerals) gave origin to life has not yet been proven, the truth is that, up to the present, biominerals are being synthetized by the organisms of different kingdoms in two basic ways: biologically induced and biologically controlled biomineralization. Paradoxically, this fact makes a fundamental difference between inorganic materials and those formed by living organisms, as the latter are associated with macromolecules that are bound to the mineral phase. Conserving growth and formation of these biogenic organic crystals inside cells is a fascinating subject that has been studied mainly in some of the kingdoms, like Monera (bacteria), Fungi (yeasts), and Animalia (Homo sapiens). Notwithstanding in the Plantae kingdom, the formation, conservation, and functions of crystals has not yet been completely elucidated and described, which is of particular relevance because life on Earth, as we know it, would not be possible without plants. The aim of the present work is to revise the different crystals of calcium oxalate synthetized inside the cells of plants, as well as to identify the mechanism of their formation and their possible functions in plants. The last part is related to the existence of certain proteins called phototropins, which not only work as the blue-light sensors, but they also play an important role on the accumulation of calcium in vacuoles. This new trend is shortly reviewed to explain the characteristics and their plausible role in the calcium uptake along with the biomineralization processes.
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Hoffmann, René, Benjamin J. Linzmeier, Kouki Kitajima, Gernot Nehrke, Martin Dietzel, Niels Jöns, Kevin Stevens y Adrian Immenhauser. "Complex Biomineralization Pathways of the Belemnite Rostrum Cause Biased Paleotemperature Estimates". Minerals 11, n.º 12 (12 de diciembre de 2021): 1406. http://dx.doi.org/10.3390/min11121406.
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Paleotemperatures based on δ18O values derived from belemnites are usually “too cold” compared to other archives and paleoclimate models. This temperature bias represents a significant obstacle in paleoceanographic research. Here we show geochemical evidence that belemnite calcite fibers are composed of two distinct low-Mg calcite phases (CP1, CP2). Phase-specific in situ measurement of δ18O values revealed a systematic offset of up to 2‰ (~8 °C), showing a lead–lag signal between both phases in analyses spaced less than 25 µm apart and a total fluctuation of 3.9‰ (~16 °C) within a 2 cm × 2 cm portion of a Megateuthis (Middle Jurassic) rostrum. We explain this geochemical offset and the lead–lag signal for both phases by the complex biomineralization of the belemnite rostrum. The biologically controlled formation of CP1 is approximating isotope fractionation conditions with ambient seawater to be used for temperature calculation. In contrast, CP2 indicates characteristic non-isotope equilibrium with ambient seawater due to its formation via an amorphous Ca-Mg carbonate precursor at high solid-to-liquid ratio, i.e., limited amounts of water were available during its transformation to calcite, thus suggesting lower formation temperatures. CP2 occludes syn vivo the primary pore space left after formation of CP1. Our findings support paleobiological interpretations of belemnites as shelf-dwelling, pelagic predators and call for a reassessment of paleoceanographic reconstructions based on belemnite stable isotope data.
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Giordani, Paolo, Paolo Modenesi y Mauro Tretiach. "Determinant factors for the formation of the calcium oxalate minerals, weddellite and whewellite, on the surface of foliose lichens". Lichenologist 35, n.º 3 (mayo de 2003): 255–70. http://dx.doi.org/10.1016/s0024-2829(03)00028-8.
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AbstractThe factors influencing the predominance of one of the two mineral forms of calcium oxalate (CO), the monohydrated whewellite (COM) and the di-hydrated weddellite (COD), forming the pruina of the upper cortex of lichens, have been investigated through a simple, sensitive histochemical assay: toluidine blue O (TBO), a metachromatic staining test. The differential reactivity of 43 thalli of 17 pruinose foliose species, supplemented by X-ray diffraction analysis and observations with polarizing and scanning electron microscopy, suggests that the histochemical reactivity of hyphal walls and cementing substances of the upper cortex are related to the density of anionic charges. These factors are probably due to the occurrence of polyuronic acid substances that strongly affects the mineralization of CO. Di-hydrated wedellite is always associated with TBO metachromatic reactivity, and COM with orthochromatic reactivity. When the material has an ambiguous ortho/metachromatic reactivity, COD and COM may occur together. This study presents the first experimental evidence that in lichens CO biomineralization is at least partially biologically controlled.
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Al-Battashi, Huda, Sanket J. Joshi, Bernhard Pracejus y Aliya Al-Ansari. "The Geomicrobiology of Chromium (VI) Pollution: Microbial Diversity and its Bioremediation Potential". Open Biotechnology Journal 10, n.º 1 (11 de noviembre de 2016): 379–89. http://dx.doi.org/10.2174/1874070701610010379.
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The role and significance of microorganisms in environmental recycling activities marks geomicrobiology one of the essential branches within the environmental biotechnology field. Naturally occurring microbes also play geo-active roles in rocks, leading to biomineralization or biomobilization of minerals and metals. Heavy metals, such as chromium (Cr), are essential micronutrients at very low concentrations, but are very toxic at higher concentrations. Generally, heavy metals are leached to the environment through natural processes or anthropogenic activities such as industrial processes, leading to pollution with serious consequences. The presence of potentially toxic heavy metals, including Cr, in soils does not necessarily result in toxicity because not all forms of metals are toxic. Microbial interaction with Cr by different mechanisms leads to its oxidation or reduction, where its toxicity could be increased or decreased. Chromite contains both Cr(III) and Fe(II) and microbial utilization of Fe(II)- Fe(III) conversion or Cr (III) - Cr (VI) could lead to the break-down of this mineral. Therefore, the extraction of chromium from its mineral as Cr (III) form increases the possibility of its oxidation and conversion to the more toxic form (Cr (VI)), either biologically or geochemically. Cr (VI) is quite toxic to plants, animals and microbes, thus its levels in the environment need to be studied and controlled properly. Several bacterial and fungal isolates showed high tolerance and resistance to toxic Cr species and they also demonstrated transformation to less toxic form Cr (III), and precipitation. The current review highlights toxicity issues associated with Cr species and environmental friendly bioremediation mediated by microorganisms.
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Lykoshin, D. D., V. V. Zaitsev, M. A. Kostromina y R. S. Esipov. "New-generation osteoplastic materials based on biological and synthetic matrices". Fine Chemical Technologies 16, n.º 1 (18 de marzo de 2021): 36–54. http://dx.doi.org/10.32362/2410-6593-2021-16-1-36-54.
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Objectives. The purpose of this analytical review is to evaluate the market for osteoplastic materials and surgical implants, as well as study the features of new-generation materials and the results of clinical applications.Methods. This review summarizes the volumes of research articles presented in the electronic database PubMed and eLIBRARY. A total of 129 scientific articles related to biological systems, calcium phosphate, polymer, and biocomposite matrices as carriers of pharmaceutical substances, primary recombinant protein osteoinductors, antibiotics, and biologically active chemical reagents were analyzed and summarized. The search depth was 10 years.Results. Demineralized bone matrix constitutes 26% of all types of osteoplastic matrices used globally in surgical osteology, which includes neurosurgery, traumatology and orthopedics, dentistry, and maxillofacial and pediatric surgery. Among the matrices, polymer and biocomposite matrices are outstanding. Special attention is paid to the possibility of immobilizing osteogenic factors and target pharmaceutical substances on the scaffold material to achieve controlled and prolonged release at the site of surgical implantation. Polymeric and biocomposite materials can retard the release of pharmaceutical substances at the implantation site, promoting a decrease in the toxicity and an improvement in the therapeutic effect. The use of composite scaffolds of different compositions in vivo results in high osteogenesis, promotes the initialization of biomineralization, and enables the tuning of the degradation rate of the material.Conclusions. Osteoplastic materials of various compositions in combination with drugs showed accelerated regeneration and mineralization of bone tissue in vivo, excluding systemic side reactions. Furthermore, although some materials have already been registered as commercial drugs, a plethora of unresolved problems remain. Due to the limited clinical studies of materials for use on humans, there is still an insufficient understanding of the toxicity of materials, time of their resorption, speed of drug delivery, and the possible long-term adverse effects of using implants of different compositions.
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Bouabdellah, Mohammed, Wissale Boukirou, Adriana Potra, Erik Melchiorre, Hassan Bouzahzah, Johan Yans, Khadra Zaid et al. "Origin of the Moroccan Touissit-Bou Beker and Jbel Bou Dahar Supergene Non-Sulfide Biomineralization and Its Relevance to Microbiological Activity, Late Miocene Uplift and Climate Changes". Minerals 11, n.º 4 (11 de abril de 2021): 401. http://dx.doi.org/10.3390/min11040401.
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Through integration of Pb-Zn ± Cu non-sulfide mineralogy, texture, and stable isotope (C, O, S) geochemistry, the world-class Touissit- Bou Beker and Jbel Bou Dahar Mississippi Valley-type districts of the Moroccan Atlasic system have been investigated in order to gain insights into the origin and processes that contributed to the formation of the base metal non-sulfide mineralization. In both districts, direct replacement (“red calamine”) and wallrock replacement (“white calamine”) ores are observed. Based on the mineral assemblages, ore textures, and crosscutting relations, three distinct mineralizing stages are recognized. The earliest, pre-non-sulfide gossanous stage was a prerequisite for the following supergene stages and constituted the driving force that ultimately promoted the leaching of most base metals such as Zn and Cu and alkalis from their rock sources. The following two stages, referred to as the main supergene “red calamine” and late “white calamine” ore stages, generated the bulk of mineable “calamine” ores in the Touissit-Bou Beker and Jbel Bou Dahar districts. Stable isotope compositions (δ13CV-PDB, δ18OV-SMOW, δ34SCDT) support a three-stage model whereby metals were released by supergene acidic fluids and then precipitated by bacteria and archaea-mediated metal-rich meteoric fluids due to a decrease in temperature and/or increase of fO2. Oxygen isotope thermometry indicates decreasing precipitation temperatures with advancing paragenetic sequence from 33° to 18 °C, with wet to semi-arid to arid climatic conditions. The close spatial relationships between coexisting sulfide and non-sulfide mineralization along with stable isotope constraints suggest that the oxidation of sulfides occurred concurrently after the main stage of the Alpine orogeny between 15 Ma and the present. More importantly, the current data show for the first time the involvement of biologically controlled activity as the major driving process that triggered both oxidation and deposition of supergene mineralization at Jbel Bou Dahar and Touissit-Bou Beker districts. Conclusions drawn from this study therefore have implications for supergene Mississippi Valley-type (MVT) -derived non-sulfide deposits worldwide and account for the prominent role of biological processes in the genesis of this category of ore deposits.
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Walton, Derek y Gordon B. Curry. "Biogeochemistry of brachiopod intracrystalline proteins and amino acids". Paleontological Society Special Publications 6 (1992): 304. http://dx.doi.org/10.1017/s2475262200008649.
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Brachiopods contain several classes of intracrystalline molecules, secreted during the growth of the organism, and subsequently incorporated in the shell during biomineralization. The function of these molecules is not clear, although in the Mollusca, molecules in similar sites are thought to be involved with biologically controlled mineralization. The order of amino acids, and hence the quantity of each amino acid in proteins is determined by the genome of the organism, and study of such molecules should reveal information regarding the genomes of the fossil organisms.Previous studies of fossil molecules from brachiopods have concentrated on the web of intracrystalline molecules which surrounds the crystallites of the secondary fibres of the shell. Work with Recent articulate brachiopods has shown that this web decays in less than a year, and hence any remnants of this web in the fossil record are likely to be highly degraded and unrepresentative of the original composition of the protein.In contrast to this, intracrystalline molecules will be protected, encased within the calcium carbonate of the shell and analogous in many ways to fluid inclusions found in inorganic minerals. In such sites, contaminant and degradative factors such as microorganisms and large concentrations of water will be excluded and the effects of the enclosing sediments negated. Any breakdown of the molecules will be in situ, and the detectable products analysed.In this study, intracrystalline molecules have been extracted from the shells of Recent and fossil brachiopods from the Plio-Pleistocene South Wanganui Basin, New Zealand. The molecules were analysed for free and peptide bound amino acids from both the soluble and insoluble fractions. The state of preservation of the molecules and their taxonomic specifity were analysed.It was found that, even in these protected sites, individual amino acids were up to 90% in the free state i.e. that the proteins had mostly been hydrolyzed by the action of time and any water remaining in the shell structure after 0.12 Ma. Amino acids which are particularly sensitive to degradative reactions, such as serine and threonine were totally lost from the soluble fraction. However, the use of multivariate statistical analyses on data from the soluble remains of the protein indicates that decay does not render the molecules useless for taxonomy; groupings can be made on the basis of analyses alone.Progressively older samples tend to have lower yields of amino acid in the soluble fraction, and this tends to correspond with an increase in the relative proportion of intracrystalline insoluble compounds. Although there is no direct linear relationship between the age of a sample and the proportion of insoluble compounds, older samples tend to have more insolubles. It is clear that other factors must play a part in the formation of these insoluble compounds. Preliminary studies of their amino acid composition indicates the presence of sensitive amino acids such as serine, indicating the stabilising effects of these diagenetic compounds.The degradation of amino acids follows complex decay pathways, with some decaying to non-amino compounds and others to other amino acids, the most common being alanine from the dehydration of serine. The increasing concentrations of these amino acids can be a distorting factor in molecular taxonomy from fossil molecules.ACKNOWLEDGEMENTS. This work was completed during the tenure of a UK NERC studentship to DW (GT4/89/GS/42) and funding from the Royal Society to GBC.
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Päßler, Jan-Filip, Emilia Jarochowska, Michel Bestmann y Axel Munnecke. "Distinguishing Biologically Controlled Calcareous Biomineralization in Fossil Organisms Using Electron Backscatter Diffraction (EBSD)". Frontiers in Earth Science 6 (28 de febrero de 2018). http://dx.doi.org/10.3389/feart.2018.00016.
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Zhang, Yuchen, Shaoyang Ma, Jiaming Nie, Zhongbo Liu, Faming Chen, Ang Li y Dandan Pei. "Journey of Mineral Precursors in Bone Mineralization: Evolution and Inspiration for Biomimetic Design". Small, 24 de agosto de 2023. http://dx.doi.org/10.1002/smll.202207951.
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AbstractBone mineralization is a ubiquitous process among vertebrates that involves a dynamic physical/chemical interplay between the organic and inorganic components of bone tissues. It is now well documented that carbonated apatite, an inorganic component of bone, is proceeded through transient amorphous mineral precursors that transforms into the crystalline mineral phase. Here, the evolution on mineral precursors from their sources to the terminus in the bone mineralization process is reviewed. How organisms tightly control each step of mineralization to drive the formation, stabilization, and phase transformation of amorphous mineral precursors in the right place, at the right time, and rate are highlighted. The paradigm shifts in biomineralization and biomaterial design strategies are intertwined, which promotes breakthroughs in biomineralization‐inspired material. The design principles and implementation methods of mineral precursor‐based biomaterials in bone graft materials such as implant coatings, bone cements, hydrogels, and nanoparticles are detailed in the present manuscript. The biologically controlled mineralization mechanisms will hold promise for overcoming the barriers to the application of biomineralization‐inspired biomaterials.
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Zhang, Zhiliang, Zhifei Zhang, Lars Holmer, Timothy P. Topper, Bing Pan y Guoxiang Li. "Evolution and diversity of biomineralized columnar architecture in early Cambrian phosphatic-shelled brachiopods". eLife 12 (10 de abril de 2024). http://dx.doi.org/10.7554/elife.88855.4.
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Biologically-controlled mineralization producing organic-inorganic composites (hard skeletons) by metazoan biomineralizers has been an evolutionary innovation since the earliest Cambrian. Among them, linguliform brachiopods are one of the key invertebrates that secrete calcium phosphate minerals to build their shells. One of the most distinct shell structures is the organo-phosphatic cylindrical column exclusive to phosphatic-shelled brachiopods, including both crown and stem groups. However, the complexity, diversity, and biomineralization processes of these microscopic columns are far from clear in brachiopod ancestors. Here, exquisitely well-preserved columnar shell ultrastructures are reported for the first time in the earliest eoobolids Latusobolus xiaoyangbaensis gen. et sp. nov. and Eoobolus acutulus sp. nov. from the Cambrian Series 2 Shuijingtuo Formation of South China. The hierarchical shell architectures, epithelial cell moulds, and the shape and size of cylindrical columns are scrutinised in these new species. Their calcium phosphate-based biomineralized shells are mainly composed of stacked sandwich columnar units. The secretion and construction of the stacked sandwich model of columnar architecture, which played a significant role in the evolution of linguliforms, is highly biologically controlled and organic-matrix mediated. Furthermore, a continuous transformation of anatomic features resulting from the growth of diverse columnar shells is revealed between Eoobolidae, Lingulellotretidae, and Acrotretida, shedding new light on the evolutionary growth and adaptive innovation of biomineralized columnar architecture among early phosphatic-shelled brachiopods during the Cambrian explosion.
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Chen, Xuefei, Wenfeng Deng, Hangfang Xiao, Yangrui Guo y Gangjian Wei. "A Perspective on Probing Coral Resilience to Climate and Environmental Changes Using Stable Isotopes of Bio‐Utilized Metal Elements". Journal of Geophysical Research: Biogeosciences 129, n.º 1 (enero de 2024). http://dx.doi.org/10.1029/2023jg007656.
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AbstractIn the face of diverse challenges like global warming, ocean acidification, and human activities, the world's coral reefs are confronting a severe ecological crisis. Understanding the historical coevolution of corals with their environment and their resilience to current climate change is crucial for protecting these ecosystems and predicting their future. In this context, metal stable isotopes in corals present a novel and alternative methodology. Their significant fractionation during coral biological processes, persistent presence in coral skeletons, and relatively straightforward sources make them a valuable tool. However, the complexity of coral biology necessitates a deeper investigation into the fundamental mechanisms behind the isotopic fractionation of these biologically utilized metal elements. A comprehensive and systematic study of the roles of metal stable elements in coral biological processes is essential. This includes examining the fractionation of metal isotopes across different parts of the corals, such as tissues, zooxanthellae, and skeletons. To achieve these goals, multidisciplinary collaborations are essential. They should focus on several key areas: interpreting metal stable isotopes data in the context of coral physiology and ecology; conducting controlled laboratory experiments on coral cultivation; engaging in comparative studies with inorganically precipitated aragonites; and developing a holistic understanding within the framework of coral biomineralization models.
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Li, Luoyang, Timothy P. Topper, Marissa J. Betts, Dorj Dorjnamjaa, Gundsambuu Altanshagai, Baktuyag Enkhbaatar, Guoxiang Li y Christian B. Skovsted. "Calcitic shells in the aragonite sea of the earliest Cambrian". Geology, 2 de noviembre de 2022. http://dx.doi.org/10.1130/g50533.1.
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The initial acquisition of calcium carbonate polymorphs (aragonite and calcite) at the onset of skeletal biomineralization by disparate metazoans across the Ediacaran-Cambrian transition is thought to be directly influenced by Earth’s seawater chemistry. It has been presumed that animal clades that first acquired mineralized skeletons during the so-called “aragonite sea” of the latest Ediacaran and earliest Cambrian (Terreneuvian) possessed aragonite or high-Mg calcite skeletons, while clades that arose in the subsequent “calcite sea” of Cambrian Series 2 acquired low-Mg calcite skeletons. Here, contrary to previous expectations, we document shells of one of the earliest helcionelloid molluscs from the basal Cambrian of southwestern Mongolia that are composed entirely of low-Mg calcite and formed during the Terreneuvian aragonite sea. The extraordinarily well-preserved Postacanthella shells have a simple prismatic microstructure identical to that of their modern low-Mg calcite molluscan relatives. High-resolution scanning electron microscope observations show that calcitic crystallites were originally encased within an intra- and interprismatic organic matrix scaffold preserved by aggregates of apatite during early diagenesis. This indicates that not all molluscan taxa during the early Cambrian produced aragonitic shells, weakening the direct link between carbonate skeletal mineralogy and ambient seawater chemistry during the early evolution of the phylum. Rather, our study suggests that skeletal mineralogy in Postacanthella was biologically controlled, possibly exerted by the associated prismatic organic matrix. The presence of calcite or aragonite mineralogy in different early Cambrian molluscan taxa indicates that the construction of calcium carbonate polymorphs at the time when skeletons first emerged may have been species dependent.