Model Of Biomineralization Research Articles

The effect of carbonate chemistry on trace elements incorporation in a high-Mg calcitic foraminifera

The sodium-to-calcium ratio (Na/Ca) of biogenic CaCO3 has recently been introduced as a proxy for past seawater Ca2+ concentrations ([Ca2+sw]) as demonstrated by a positive correlation between seawater and shell Na/Ca with minor influence of salinity. In the present study, we investigate the effect of carbonate chemistry on the Na/Ca proxy by conducting a set of experiments independently varying pH and the concentration of dissolved inorganic carbon (DIC). In addition to Na+, the incorporation of Li+, Mg2+, and Sr2+ into the shells of the large benthic high-Mg calcitic foraminifer Operculina ammonoides was assessed by culturing under constant DIC (∼2170 µmol kg−1) with varying pH (7.5–8.4 NBS scale), and under varying DIC (830–2470 µmol kg−1) with constant pH (∼7.9). Foraminiferal growth rate correlates linearly with calcite saturation state (Ω) of the experimental seawater (SW). The lowest pH and DIC experiments show low population growth rates, and some of these specimens died and their shells partially dissolved.Na/Cashell and Li/Cashell in O. ammonoides are positively correlated with SW [CO32–] and Ω, whereas Sr/Cashell and Mg/Cashell are much less sensitive to these parameters. The relative sensitivity of Na/Cashell to Ω in O. ammonoides is ∼ 4 % per Ω unit. However, given that past changes in surface water Ω were probably small relative to changes in [Ca2+sw] the correction for this secondary effect over the Cenozoic is likely to be small. Therefore, we conclude that O. ammonoides Na/Ca sensitivity to the carbonate system is unlikely to compromise the use of this proxy to reconstruct past [Ca2+sw]. In the case of the low-Mg planktic and benthic foraminifera, a data compilation exercise indicates that no resolvable carbonate chemistry effect exists on Na/Ca. Thus, the Na/Ca proxy in benthic nummulitid and planktic foraminifera can be utilized for past [Ca2+sw] reconstructions. Furthermore, coupling this information with the distribution coefficients of other elemental and isotopic systems (e.g., Li+, Sr2+, Mg2+, K+, B, δ11B) may allow the reconstruction of wider aspects of past ocean chemistry. Finally, comparison of trace and minor element incorporation into low and high-Mg foraminiferal species, coccolithophores, inorganic calcite, and amorphous CaCO3 (ACC), we propose a modified biomineralization model for hyaline foraminifera centered on SW vacuolization. Foraminiferal data can be explained by a biomineralization process in which high-Mg species utilize a precursor phase (ACC) to produce high-Mg calcite whereas low-Mg species actively remove Mg2+ from the site of calcification.

Intrinsic and extrinsic determinants of conditional localization of Mms6 to magnetosome organelles in Magnetospirillum magneticum AMB-1.

Magnetotactic bacteria are a diverse group of microbes that use magnetic particles housed within intracellular lipid-bounded magnetosome organelles to guide navigation along geomagnetic fields. The development of magnetosomes and their magnetic crystals in Magnetospirillum magneticum AMB-1 requires the coordinated action of numerous proteins. Most proteins are thought to localize to magnetosomes during the initial stages of organelle biogenesis, regardless of environmental conditions. However, the magnetite-shaping protein Mms6 is only found in magnetosomes that contain magnetic particles, suggesting that it might conditionally localize after the formation of magnetosome membranes. The mechanisms for this unusual mode of localization to magnetosomes are unclear. Here, using pulse-chase labeling, we show that Mms6 translated under non-biomineralization conditions translocates to pre-formed magnetosomes when cells are shifted to biomineralizing conditions. Genes essential for magnetite production, namely mamE, mamM, and mamO, are necessary for Mms6 localization, whereas mamN inhibits Mms6 localization. MamD localization was also investigated and found to be controlled by similar cellular factors. The membrane localization of Mms6 is dependent on a glycine-leucine repeat region, while the N-terminal domain of Mms6 is necessary for retention in the cytosol and impacts conditional localization to magnetosomes. The N-terminal domain is also sufficient to impart conditional magnetosome localization to MmsF, altering its native constitutive magnetosome localization. Our work illuminates an alternative mode of protein localization to magnetosomes in which Mms6 and MamD are excluded from magnetosomes by MamN until biomineralization initiates, whereupon they translocate into magnetosome membranes to control the development of growing magnetite crystals.IMPORTANCEMagnetotactic bacteria (MTB) are a diverse group of bacteria that form magnetic nanoparticles surrounded by membranous organelles. MTB are widespread and serve as a model for bacterial organelle formation and biomineralization. Magnetosomes require a specific cohort of proteins to enable magnetite formation, but how those proteins are localized to magnetosome membranes is unclear. Here, we investigate protein localization using pulse-chase microscopy and find a system of protein coordination dependent on biomineralization-permissible conditions. In addition, our findings highlight a protein domain that alters the localization behavior of magnetosome proteins. Utilization of this protein domain may provide a synthetic route for conditional functionalization of magnetosomes for biotechnological applications.

A Perspective on Probing Coral Resilience to Climate and Environmental Changes Using Stable Isotopes of Bio‐Utilized Metal Elements

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.

Formation of the Outer Shell Layer in Pinctada margaritifera: Structural and Biochemical Evidence for a Sequential Development of the Calcite Units

Calcite prismatic units that form the outer layers of “nacro-prismatic” Pelecypod shells are often used as biomineralization models due to their individual size, simple shape, and spatial arrangement. However, these models do not take into account the developmental history of the shell. After metamorphosis, a series of structural changes predating production of the prisms is commonly missing. Consequently, this study focuses on the early stages of the calcite biomineralization area of the Pinctada margaritifera as it occurs in the outer mantle groove. It also includes the structural changes following the typical “simple prism” status. The interpretation takes advantage of an ancient result from genomic investigations: the localisation of Prisilkin-39, a protein associated with production of the calcite units. A revision of the initial interpretation concerning the position of this Prisilkin-39-producing area provides additional evidence of the role of two distinct mineralizing sectors in the formation of the calcite units in the Pinctada shell: the outer mantle groove and the anterior mineralizing area of the shell mantle.

Effect of linearly polarized microwaves on nanomorphology of calcium carbonate mineralization using peptides

Microwaves are used for diverse applications such as mobile phones, ovens, and therapy devices. However, there are few reports on the effects of microwaves on diseases other than cancer, and on physiological processes. Here, we focused on CaCO3 mineralization as a model of biomineralization and attempted to elucidate the effect of microwaves on CaCO3 mineralization using peptides. We conducted AFM, ζ potential, HPLC, ICP-AES, and relative permittivity measurements. Our findings show that microwaves alter the nanomorphology of the CaCO3 precipitate, from sphere-like particles to string-like structures. Furthermore, microwaves have little effect on the mineralization when the mineralization ability of a peptide is high, but a large effect when the precipitation ability is low. Our findings may be applicable to not only the treatment of teeth and bones but also the development of organic–inorganic nanobiomaterials. This methodology can be expanded to other molecular/atomic reactions under various microwave conditions to alter reaction activity parameters.

Bacterial mineralization of chromium-copper spinel with highly performance in electroplating effluent

Cr (VI) contamination has posed severe challenges to water quality, food safety, and land resources. Microbial reduction of Cr(VI) to Cr(III) has drawn considerable attention due to its low cost and environmental friendliness. However, recent reports have shown that Cr(VI) generates highly migratable organo-Cr(III) rather than stable inorganic chromium minerals during the biological reduction process. In this work, it was reported for the first time that spinel structure CuCr2O4 was formed by Bacillus cereus in Cr biomineralization process. Different from known biomineralization models (biologically controlled mineralization and biologically induced mineralization), the chromium-copper minerals here appeared as specialized minerals with extracellular distribution. In view of this, a possible mechanism of biologically secretory mineralization was proposed. In addition, Bacillus cereus demonstrated a high conversion ability in the treatment of electroplating wastewater. The Cr(VI) removal percentage reached 99.7%, which satisfied the Chinese emission standard of pollutants for electroplating (GB 21,900–2008), indicating its application potential. Altogether, our work elucidated a bacterial chromium spinel mineralization pathway and evaluated the potential of this system for application in actual wastewater, opening a new avenue in the field of chromium pollution treatment and control.

The Caudofoveata (Mollusca) Spicule as a Biomineralization Model: Unique Features Revealed by Combined Microscopy Methods

Caudofoveates are benthic organisms that reside in the deep waters of continental slopes in the world. They are considered to be a group that is of phylogenetic and ecological importance for the phylum Mollusca. However, they remain poorly studied. In this work, we revealed the structure of the spicules of Caudofoveatan mollusks Falcidens sp. The spicules presented a hierarchical organization pattern across different length scales. Various imaging and analytical methods related to light and electron microscopy were employed to characterize the samples. The primary imaging methods utilized included: low voltage field emission scanning electron microscopy (FEG-SEM), focused ion beam-scanning electron microscopy (FIB-SEM), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and electron diffraction. In addition, we performed a physicochemical analysis by electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDS). A crucial factor for successfully obtaining the results was the preparation of lamellae from the spicules without damaging the original structures, achieved using FIB-SEM. This allowed us to obtain diffraction patterns of significant areas of well-preserved sections (lamellae) of the spicules in specific directions and demonstrate for the first time that the bulk of these structures is organized as a single crystal of calcium carbonate aragonite. On the other hand, AFM imaging of the spicules’ dorsal surface revealed a wavy appearance, composed of myriads of small, pointed crystallites oriented along the spicules’ longer axis (i.e., the c-axis of the aragonite). The organization pattern of these small crystallites, the possible presence of twins, the relationship between confinement conditions and accessory ions in the preference for mineral polymorphs, and the single crystalline appearance of the entire spicule, along with the observation of growth lines, provide support for further studies employing Caudofoveata spicules as a model for biomineralization studies.

A NOVEL SPHEROIDAL PROGENITOR CELL DIFFERENTIATION AND BONE-LIKE IN VITRO BIOMINERALIZATION MODEL

Many age-related diseases affect our skeletal system, but bone health-targeting drug development strategies still largely rely on 2D in vitro screenings. We aimed at developing a scaffold-free progenitor cell-based 3D biomineralization model for more physiological high-throughput screenings.MC3T3-E1 pre-osteoblast spheroids were cultured in V-shaped plates for 28 days in alpha-MEM (10% FCS, 1% L-Gln, 1X NEAA) with 1% pen/strep, changed every two days, and differentiation was induced by 10mM b-glycerophosphate and 50µg/ml ascorbic-acid. Osteogenic cell differentiation was assessed through profiling mRNA expression of selected osteogenic markers by efficiency corrected normalized 2^DDCq RT-qPCR. Biomineralization in spheroids was evaluated by histochemistry (Alizarin Red/von Kossa staining), Alkaline phosphatase (Alp) activity, Fourier transform infrared spectroscopy (FTIR) analyses, micro-CT analyses, and scanning electron microscopy on critical point-dried samples. GraphPad Prism 9 analyses comprised Shapiro-Wilk and Brown-Forsythe tests as well as 2-way ANOVA with Tukey post-hoc and non-parametric Kruskal-Wallis with Dunn post-hoc tests.During mineralization, as opposed to non-mineralizing conditions, characteristic mRNA expression profiles of selected early and late osteoblast differentiation markers (e.g., RunX, Alp, Col1a1, Bglap) were observed between day 0 and 28 of culture; Alp was strongly upregulated (p<0.001) from day 7 on, followed by its enzymatic activity (p<0.001). Bglap and Col1a1 expression peaked on (p<0.001) and from day 14 on (p<0.05), respectively. IHC revealed osteocalcin staining in the spheroid core regions at day 14, while type I collagen staining of the cores was most prominent from day 21 on. Alizarin Red and Von Kossa confirmed central and radially outwards expanding mineralization patterns between day 14 and day 28, which was accompanied by a steady increase in extracellular calcium deposition over time (p<0.001). Micro-CT analyses allowed quantitative appreciation of the overall increase in mineral density over time (day21, p<0.05; d28, p<0.001), while SEM-EDX and FTIR ultimately confirmed a bone-like hydroxyapatite mineral deposition in 3D.A novel and thoroughly characterized versatile bone-like 3D biomineralization in vitro model was established, which allows for studying effects of pharmacological interventions on bone mineralization ex vivo under physiomimetic conditions. Ongoing studies currently aim at elucidating in how far it specifically recapitulates intramembranous ossification.

Genome-wide association study analysis to resolve the key regulatory mechanism of biomineralization in Pinctada fucata martensii.

Biomineralization-controlled exo-/endoskeleton growth contributes to body growth and body size diversity. Molluscan shells undergo ectopic biomineralization to form the exoskeleton and biocalcified "pearl" involved in invading defence. Notably, exo-/endoskeletons have a common ancestral origin, but their regulation and body growth are largely unknown. This study employed the pearl oyster, Pinctada fucata marntensii, a widely used experimental model for biomineralization in invertebrates, to perform whole-genome resequencing of 878 individuals from wild and breeding populations. This study characterized the genetic architecture of biomineralization-controlled growth and ectopic biomineralization. The insulin-like growth factor (IGF) endocrine signal interacted with ancient single-copy transcription factors to form the regulatory network. Moreover, the "cross-phylum" regulation of key long noncoding RNA (lncRNA) in bivalves and mammals indicated the conserved genetic and epigenetic regulation in exo-/endoskeleton growth. Thyroid hormone signal and apoptosis regulation in pearl oysters affected ectopic biomineralization in pearl oyster. These findings provide insights into the mechanism underlying the evolution and regulation of biomineralization in exo-/endoskeleton animals and ectopic biomineralization.

Physiological Mineralization during In Vitro Osteogenesis in a Biomimetic Spheroid Culture Model.

Bone health-targeting drug development strategies still largely rely on inferior 2D in vitro screenings. We aimed at developing a scaffold-free progenitor cell-based 3D biomineralization model for more physiological high-throughput screenings. MC3T3-E1 pre-osteoblasts were cultured in α-MEM with 10% FCS, at 37 °C and 5% CO2 for up to 28 days, in non-adherent V-shaped plates to form uniformly sized 3D spheroids. Osteogenic differentiation was induced by 10 mM β-glycerophosphate and 50 µg/mL ascorbic acid. Mineralization stages were assessed through studying expression of marker genes, alkaline phosphatase activity, and calcium deposition by histochemistry. Mineralization quality was evaluated by Fourier transformed infrared (FTIR) and scanning electron microscopic (SEM) analyses and quantified by micro-CT analyses. Expression profiles of selected early- and late-stage osteoblast differentiation markers indicated a well-developed 3D biomineralization process with strongly upregulated Col1a1, Bglap and Alpl mRNA levels and type I collagen- and osteocalcin-positive immunohistochemistry (IHC). A dynamic biomineralization process with increasing mineral densities was observed during the second half of the culture period. SEM–Energy-Dispersive X-ray analyses (EDX) and FTIR ultimately confirmed a native bone-like hydroxyapatite mineral deposition ex vivo. We thus established a robust and versatile biomimetic, and high-throughput compatible, cost-efficient spheroid culture model with a native bone-like mineralization for improved pharmacological ex vivo screenings.

Precipitation of calcium carbonate in the presence of rhamnolipids in alginate hydrogels as a model of biomineralization

This paper reports the effects of rhamnolipids presence in the alginate hydrogel and CO32- solution, on the precipitation of CaCO3 in the Ca2+ loaded alginate hydrogel. Characteristics of the formed particles are discussed. Model conditions containing alginate hydrogel and rhamnolipids were used in order to mimic the natural environment of biomineralization in biofilms. It has been shown that rhamnolipids affect the characteristics of precipitated calcium carbonate effect of using these biosurfactants depends on their concentration as well as whether they are directly present in the hydrogel matrix or the carbonate solution surrounding the hydrogel. The greatest effect compared to the control samples was found for the rhamnolipids in the form of micelles directly present in the hydrogel with the CaCl2 cross-linked solution at concentration of 0.05 M. These conditions result in the highest increase in vaterite content, specific surface area, and pore volume. The mechanism of CaCO3 precipitation in alginate hydrogel containing rhamnolipids has been proposed.

The mineralization and early diagenesis of deep-sea coral Madrepora oculata

The skeletons of aragonitic corals carry essential information about oceanic environmental changes in the past. However, coral-based geochemical proxies are sensitive to vital effect and post-depositional diagenetic processes, which have not been well understood for deep-sea corals. In this study, we have investigated the mineralization and early diagenetic process of the dendroid stem of a dead deep-sea scleractinian coral sample (Madrepora oculata) collected by Remote Operated Vehicle (ROV) from a seamount in the Caroline Ridge, western Pacific. Despite being only ~270 years old, as dated by the U-series disequilibrium method, this sample already has extensive diagenesis including a visible chalky layer. The outermost chalky layer and the adjacent pristine skeleton of the sample were characterized by multiple mineralogical (SEM, XRD, EBSD, Raman Spectroscopy) and geochemical (ICP-OES, LA-ICP-MS, IR-MS, MC-ICP-MS) techniques. Skeletal stable C and O isotopes display strong linearity, with a trend pointing toward the theoretical isotopic composition of inorganically-precipitated aragonite from local seawater. This observation suggests that the epithecal mineralization of M. oculata is far from equilibrium with seawater and can be quantitatively explained by bio-mineralization models developed for solitary scleractinian corals. We further show that chalking of the outer layer, a common feature in sub-fossilized deep-sea corals, is caused by microbial-driven boring and μm-scale dissolution voids at an average rate of 3.5 μmol/cm2/y (scaled to the skeleton surface) without notable secondary infillings or mineralogical alternations. The higher average δ13C and δ18O of the chalky part than the pristine part might be due to the preferential dissolution of carbonate relatively depleted in 13C and 18O during alteration, and/or reduced isotope fractionation from seawater during coral mineralization of the outer layer. The chalky layer shows significantly higher Mn/Ca and Th/Ca ratios than the pristine part, characterized by Th/Mn ratios similar to that of the dissolved component of local seawater. Our study suggests that the incorporation of external Th into the coral skeleton is most likely associated with organic binding rather than detrital contamination, secondary carbonate mineral formation, adsorption onto surfaces of chalky aragonite or ferromanganese oxides, with important implications for coral U-series geochronology.

Mesocrystalline Architecture in Hyaline Foraminifer Shells Indicates a Non‐Classical Crystallisation Pathway

AbstractCalcareous foraminifer shells (tests) represent one of the most important archives for paleoenvironmental and paleoclimatic reconstruction. To develop a mechanistic understanding of the relationship between environmental parameters and proxy signals, knowledge of the fundamental processes operating during foraminiferal biomineralization is essential. Here, we apply microscopic and diffraction‐based methods to address the crystallographic and hierarchical structure of the test wall of different hyaline foraminifer species. Our results show that the tests are constructed from micrometer‐scale oriented mesocrystals built of nanometer‐scale entities. Based on these observations, we propose a mechanistic extension to the biomineralization model for hyaline foraminifers, centered on the formation and assembly of units of metastable carbonate phases to the final mesocrystal via a non‐classical particle attachment process, possibly facilitated by organic matter. This implies the presence of metastable precursors such as vaterite or amorphous calcium carbonate, along with phase transitions to calcite, which is relevant for the mechanistic understanding of proxy incorporation in the hyaline foraminifers.

Oxygen isotopes of calcite precipitated at high ionic strength: CaCO3-DIC fractionation and carbonic anhydrase inhibition

Background electrolytes affect calcite precipitation and dissolution rates and hence have the potential to impact kinetic isotope fractionation between calcite and the dissolved inorganic carbon (DIC) species. We grew inorganic calcite from NaCl-CaCl2 solutions (T = 25 °C, pH = 8.3, and crystal growth rate = 10−6.3 ± 0.3 mol m−2 s−1) to test for potential ionic strength effects on the oxygen isotope fractionation between calcite and an isotopically equilibrated inorganic carbon pool (αc/EIC). Calcite was grown in the presence of the enzyme carbonic anhydrase from bovine erythrocytes (bCA) to promote isotopic equilibration of the DIC pool.No evidence of an ionic strength effect on αc/EIC was found for NaCl concentrations up to 0.35 M (1000lnαc/w = 28.0 ± 0.1; n = 7). For experiments conducted with [NaCl] > 0.35 M, the DIC pool could not be maintained in isotopic equilibrium with water due to the inhibitory effect of NaCl on bCA. The use of other types of CA may be required to maintain isotopic equilibration of DIC in solution with ionic strength close to or above that of seawater.The oxygen isotope results were modeled successfully with an isotopic box model for a CO2-fed solution that tracks the isotopic composition of each DIC species and CaCO3. The experimental and modeling results suggest that the efficacy of bCA decreases exponentially with increasing [NaCl]. We quantify the salt effect on the quantity kcat/KM, which relates the catalyzed rate constant for CO2 hydration to the concentration of bCA. The salt effect can be implemented in models of biomineralization with potential to extend our knowledge of oxygen isotope vital effects in marine organisms.

The primary controls on U/Ca and minor element proxies in a cold-water coral cultured under decoupled carbonate chemistry conditions

Culture experiments are uniquely suited for uncovering the fundamental factors controlling skeletal geochemistry because it is possible to explore conditions beyond what is found in the modern ocean and to decouple parameters that co-vary in nature. We cultured juvenile individuals of a cold-water coral (Balanophyllia elegans) in a set of experiments that decoupled carbonate chemistry parameters over a wide range of pH, DIC, and [CO32−] values. Using a multi-element mixed spike isotope dilution method we then analyzed cultured skeletons for U/Ca, which has been proposed as a potential proxy for seawater pH and [CO32−], as well as Sr/Ca, and Mg/Ca.We find that U/Ca and Sr/Ca ratios in cultured B. elegans are most strongly correlated with solution DIC and not pH or [CO32−]. We also confirm previous observations that Metal/Calcium (Me/Ca) ratios follow the same correlated relationships between and among individuals across different experimental conditions. Interpretation of these robust Me/Ca patterns within the framework of a geochemical model of biomineralization allows us to identify two “rules” of skeletal growth for B. elegans. First, changes in seawater exchange rates can explain variability in B. elegans Me/Ca ratios, correlations between these ratios, and sensitivity of Me/Ca to changes in seawater carbonate chemistry. Second, our model best fits our data if we assume that calcifying fluid pH for B. elegans remains constant across widely varying experimental seawater compositions. Our study has implications for the recently developed Sr-U paleothermometer because it refines our understanding of the environmental parameters affecting this proxy. Our model further demonstrates that U/Ca is not a robust indicator of seawater pH or [CO32−]. Instead, U/Ca may record how calcifying fluid [CO32−] responds to changes in the environment or calcification dynamics, which may be useful in evaluating how corals respond to changes like ocean acidification. Measurements of U/Ca and additional Me/Ca ratios in other coral species, evaluated within a similar framework, may elucidate how those species respond to environmental change.

Iron(II) reactions with glycine – suitable biomineralization model?

The reactions of Mohr’s salt with amino acid glycine in aqueous solution and aerobic conditions were studied and obtained samples consist of different compounds. The obtained products were characterized by elemental analysis, infrared spectroscopy and the iron determination also and exhibited very low organic matter content – the sum of N, C, H and S content less than 20 % and Fe content around 40 %. Prepared samples consist of iron(II) amino acid complex [Fe(glyH)(SO4)]n, known as iron food supplement (FeGS) as the only sulphur containing compound. Its content varies from 26 % up to 46 %. Ferrous glycinate was obtained in the samples collected initially after the reaction in very low content < 7 %. Iron(III) hydroxy-oxide FeO(OH) was obtained in the range 40 – 65 %. The FeO(OH) content increased with the decreasing FeGS content. Formation of inorganic FeO(OH) suggest the ongoing redox reaction under aerobic condition therefore, it is suggested as a biomineralization reaction model.

Calcite as a Precursor of Hydroxyapatite in the Early Biomineralization of Differentiating Human Bone-Marrow Mesenchymal Stem Cells.

Biomineralization is the process by which living organisms generate organized mineral crystals. In human cells, this phenomenon culminates with the formation of hydroxyapatite, which is a naturally occurring mineral form of calcium apatite. The mechanism that explains the genesis within the cell and the propagation of the mineral in the extracellular matrix still remains largely unexplained, and its characterization is highly controversial, especially in humans. In fact, up to now, biomineralization core knowledge has been provided by investigations on the advanced phases of this process. In this study, we characterize the contents of calcium depositions in human bone mesenchymal stem cells exposed to an osteogenic cocktail for 4 and 10 days using synchrotron-based cryo-soft-X-ray tomography and cryo-XANES microscopy. The reported results suggest crystalline calcite as a precursor of hydroxyapatite depositions within the cells in the biomineralization process. In particular, both calcite and hydroxyapatite were detected within the cell during the early phase of osteogenic differentiation. This striking finding may redefine most of the biomineralization models published so far, taking into account that they have been formulated using murine samples while studies in human cell lines are still scarce.

Study on the Crystal Structure and Genetic Structure of Eggshell

Eggshell provides a relatively independent and stable internal environment for embryo growth and development, and is also a source of calcium ions required for embryo development. Eggshells of good quality can reduce the risk of food safety to a certain extent, and can also reduce the economic losses caused by broken eggshells and improve economic efficiency. At the same time, the process of eggshell formation is also a classic biomineralization model. In this study, the 600K high-density SNP chip of chicken was used to perform SNP typing on several groups obtained by the reciprocal cross between Bailaihang and Dongxiang green-shell hens. Scanning electron microscopy and X-ray crystal diffraction were used to determine the ultrastructure and eggshell ultrastructure. Crystal structure, explain its genetic basis, and explore the relationship between eggshell ultrastructure and crystal structure. This study believes that the DERA gene plays an important role in regulating the growth of eggshell crystals. There are three possible ways of action: one is to provide energy for the synthesis of uterine tissue cell matrix protein and its transport with ions; the second is to reduce the stress of high Ca2+ concentration stress, maintain cell activity, and for the growth of eggshell crystals Stably provide the required Ca2+; third, by regulating the concentration of ATP in the uterine fluid, the effect on the growth of eggshell crystals.

Controls on boron isotopes in a cold-water coral and the cost of resilience to ocean acidification

Coral skeletal growth is sensitive to environmental change and may be adversely impacted by an acidifying ocean. However, physiological processes can also buffer biomineralization from external conditions, providing apparent resilience to acidification in some species. These same physiological processes affect skeletal composition and can impact paleoenvironmental proxies. Understanding the mechanisms of coral calcification is thus crucial for predicting the vulnerability of different corals to ocean acidification and for accurately interpreting coral-based climate records. Here, using boron isotope (δ11B) measurements on cultured cold-water corals, we explain fundamental features of coral calcification and its sensitivity to environmental change. Boron isotopes are one of the most widely used proxies for past seawater pH, and we observe the expected sensitivity between δ11B and pH. Surprisingly, we also discover that coral δ11B is independently sensitive to seawater dissolved inorganic carbon (DIC). We can explain this new DIC effect if we introduce boric acid diffusion across cell membranes as a new flux within a geochemical model of biomineralization. This model independently predicts the sensitivity of the δ11B-pH proxy, without being trained to these data, even though calcifying fluid pH (pHCF) is constant. Boric acid diffusion can resolve why δ11B is a useful proxy across a range of calcifiers, including foraminifera, even when calcifying fluid pH differs from seawater. Our modeling shows that δ11B cannot be interpreted unequivocally as a direct tracer of pHCF. Constant pHCF implies similar calcification rates as seawater pH decreases, which can explain the resilience of some corals to ocean acidification. However, we show that this resilience has a hidden energetic cost such that calcification becomes less efficient in an acidifying ocean.

Avian eggshell formation reveals a new paradigm for vertebrate mineralization via vesicular amorphous calcium carbonate

Amorphous calcium carbonate (ACC) is an unstable mineral phase, which is progressively transformed into aragonite or calcite in biomineralization of marine invertebrate shells or avian eggshells, respectively. We have previously proposed a model of vesicular transport to provide stabilized ACC in chicken uterine fluid where eggshell mineralization takes place. Herein, we report further experimental support for this model. We confirmed the presence of extracellular vesicles (EVs) using transmission EM and showed high levels of mRNA of vesicular markers in the oviduct segments where eggshell mineralization occurs. We also demonstrate that EVs contain ACC in uterine fluid using spectroscopic analysis. Moreover, proteomics and immunofluorescence confirmed the presence of major vesicular, mineralization-specific and eggshell matrix proteins in the uterus and in purified EVs. We propose a comprehensive role for EVs in eggshell mineralization, in which annexins transfer calcium into vesicles and carbonic anhydrase 4 catalyzes the formation of bicarbonate ions (HCO[Formula: see text]), for accumulation of ACC in vesicles. We hypothesize that ACC is stabilized by ovalbumin and/or lysozyme or additional vesicle proteins identified in this study. Finally, EDIL3 and MFGE8 are proposed to serve as guidance molecules to target EVs to the mineralization site. We therefore report for the first-time experimental evidence for the components of vesicular transport to supply ACC in a vertebrate model of biomineralization.