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ABSTRACT Corals residing in habitats that experience high‐frequency seawater pCO2 variability may possess an enhanced capacity to cope with ocean acidification, yet we lack a clear understanding of the molecular toolkit enabling acclimatisation to environmental extremes or how life‐long exposure to pCO2 variability influences biomineralisation. Here, we examined the gene expression responses and micro‐skeletal characteristics of Pocillopora damicornis originating from the reef flat and reef slope of Heron Island, southern Great Barrier Reef. The reef flat and reef slope had similar mean seawater pCO2, but the reef flat experienced twice the mean daily pCO2 amplitude (range of 797 v. 399 μatm day−1, respectively). A controlled mesocosm experiment was conducted over 8 weeks, exposing P. damicornis from the reef slope and reef flat to stable (218 ± 9) or variable (911 ± 31) diel pCO2 fluctuations (μatm; mean ± SE). At the end of the exposure, P. damicornis originating from the reef flat demonstrated frontloading of 25% of the expressed genes regardless of treatment conditions, suggesting constitutive upregulation. This included higher expression of critical biomineralisation‐related genes such as carbonic anhydrases, skeletal organic matrix proteins, and bicarbonate transporters. The observed frontloading corresponded with a 40% increase of the fastest deposited areas of the skeleton in reef flat corals grown under non‐native, stable pCO2 conditions compared to reef slope conspecifics, suggesting a compensatory response that stems from acclimatisation to environmental extremes and/or relief from stressful pCO2 fluctuations. Under escalating ocean warming and acidification, corals acclimated to environmental variability warrant focused investigation and represent ideal candidates for active interventions to build reef resilience while societies adopt strict policies to limit climate change. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles offer many exciting possibilities in biomedicine, from cell imaging to cancer treatment. One of the currently researched nanoparticles are magnetosomes, magnetite nanoparticles of high chemical purity synthesized by magnetotactic bacteria. Despite their therapeutic potential, very little is known about their degradation in human cells, and even less so of their degradation within tumours. In an effort to explore the potential of magnetosomes for cancer treatment, we have explored their degradation process in a 3D human lung carcinoma model at the subcellular level and with nanometre scale resolution. We have used state of the art hard X-ray probes (nano-XANES and nano-XRF), which allow for identification of distinct iron phases in each region of the cell. Our results reveal the progression of magnetite oxidation to maghemite within magnetosomes, and the biosynthesis of magnetite and ferrihydrite by ferritin. [ABSTRACT FROM AUTHOR]

Abstract Magnetic nanoparticles offer many exciting possibilities in biomedicine, from cell imaging to cancer treatment. One of the currently researched nanoparticles are magnetosomes, magnetite nanoparticles of high chemical purity synthesized by magnetotactic bacteria. Despite their therapeutic potential, very little is known about their degradation in human cells, and even less so of their degradation within tumours. In an effort to explore the potential of magnetosomes for cancer treatment, we have explored their degradation process in a 3D human lung carcinoma model at the subcellular level and with nanometre scale resolution. We have used state of the art hard X-ray probes (nano-XANES and nano-XRF), which allow for identification of distinct iron phases in each region of the cell. Our results reveal the progression of magnetite oxidation to maghemite within magnetosomes, and the biosynthesis of magnetite and ferrihydrite by ferritin. Graphical Abstract

This paper builds on exploring the applications of biomediated pathways to solve geotechnical challenges. First, the state of the art of biological remediation strategies including microbial remediation and phytoremediation have been introduced and critically reviewed in the context of decontaminating the soils. Next, biopolymerisation, biomineralisation and bioneutralisation processes have been depicted with a special emphasis on the applications including but not limited to soil stabilisation, soil erosion prevention, anti-desertification and pH neutralisation. Each of these methods have their own limitations and bottlenecks while scaling up, and these challenges have been summarised and some possible paths to overcome the challenges have also been discussed. The state of the art of electromagnetic (EM) monitoring methods to capture the effects of biomediation on spatio-temporal soil properties are then highlighted as a non-invasive and rapid pathway to track the progress of biomediated soil processes. Finally, each of the technologies discussed have been evaluated for their maturity level using the principles of technology readiness level (TRL). A majority of the technologies amounting to around 77% are still in the TRL 4–7, i.e. in the valley of death. It is thus evident that development of these technologies needs to be supported with appropriate funding for improving their maturity to a level of industrial deployment.

Amidst the increasing significance of innovative solutions for bioremediation of heavy metal removal, this paper offers a thorough bibliometric analysis of microbial-induced carbonate precipitation (MICP) for heavy metal removal, as a promising technology to tackle this urgent environmental issue. This study focused on articles published from 1999 to 2022 in the Scopus database. It assesses trends, participation, and key players within the MICP for heavy metal sequestration. Among the 930 identified articles, 74 countries participated in the field, with China being the most productive. Varenyam Achal, the Chinese Academy of Sciences, and Chemosphere are leaders in the research landscape. Using VOSviewer and R-Studio, keyword hotspots like "MICP", "urease", and "heavy metals" underscore the interdisciplinary nature of MICP research and its focus on addressing a wide array of environmental and soil-related challenges. VOSviewer emphasises essential terms like "calcium carbonate crystal", while R-Studio highlights ongoing themes such as "soil" and "organic" aspects. These analyses further showcase the interdisciplinary nature of MICP research, addressing a wide range of environmental challenges and indicating evolving trends in the field. This review also discusses the literature concerning the potential of MICP to immobilise contaminants, the evolution of the research outcome in the last two decades, MICP treatment techniques for heavy metal removal, and critical challenges when scaling from laboratory to field. Readers will find this analysis beneficial in gaining valuable insights into the evolving field and providing a solid foundation for future research and practical implementation. [ABSTRACT FROM AUTHOR]

Coral skeletal B/Ca (effectively B/CO 3 2–), in combination with boron isotopic composition (δ11B), has been used to reconstruct the dissolved inorganic carbon chemistry of coral calcification media and to explore the biomineralisation process and its response to ocean acidification. This approach assumes that B(OH) 4 −, the B species incorporated into aragonite, competes with dissolved inorganic carbon species for inclusion in the mineral lattice. In this study we precipitated aragonite from seawater in vitro under conditions that simulate the compositions of the calcification media used to build tropical coral skeletons. To deconvolve the effects of pH and [CO 3 2–] on boron incorporation we conducted multiple experiments at constant [CO 3 2–] but variable pH and at constant pH but variable [CO 3 2–], both in the absence and presence of common coral skeletal amino acids. Large changes in solution [CO 3 2–], from < 400 to >1000 µmol kg−1, or in precipitation rate, have no significant effect on aragonite B/Ca at pH total of 8.20 and 8.41. A significant inverse relationship is observed between solution [CO 3 2–] and aragonite B/Ca at pH total = 8.59. Aragonite B/Ca is positively correlated with seawater pH across precipitations conducted at multiple pH but this relationship is driven by the effect of pH on the abundance of B(OH) 4 – in seawater. Glutamic acid and glycine enhance the incorporation of B in aragonite but aspartic acid has no measurable effect. Normalising aragonite B/Ca to solution [B(OH) 4 –] creates K D B(OH)4− which do not vary significantly between pH treatments. This implies that B(OH) 4 – and CO 3 2– do not compete with each other for inclusion in the aragonite lattice at pH total 8.20 and 8.41. Only at high pH (8.59), when [B(OH) 4 –] is high, do we observe evidence to suggest that the 2 anions compete to be incorporated into the lattice. These high pH conditions represent the uppermost limits reliably measured in the calcification media of tropical corals cultured under present day conditions, suggesting that skeletal B/Ca may not reflect the calcification media dissolved inorganic carbon chemistry in all modern day corals. [ABSTRACT FROM AUTHOR]

In the present work, grain‐refined WE43 magnesium alloy was produced by friction stir processing to investigate the in vitro degradation behavior targeted for temporary bone implant applications. Friction stir processing resulted in significant grain refinement (from 46±4.2 μm to 16.1±5.4 μm) as observed from microstructural studies. Increased wettability was observed from the contact angle measurements in grain‐refined WE43 alloy. The corrosion behavior of the base alloy and the grain refined alloy assessed by potentiodynamic polarization tests demonstrated the influence of the smaller grain size and decreased intermetallics on enhancing corrosion resistance. Immersion studies carried out in simulated body fluids for one week indicated a quick development of the protective magnesium hydroxide on the surface of grain‐refined WE43 alloy compared with the base alloy. The deposition of the mineral phases from the immersed solution on the surface of the samples was studied by scanning electron microscopy and x‐ray diffraction analysis to assess the effect of microstructure on the biomineralization. Promisingly, grain refined WE43 exhibited relatively excellent mineral deposition which further helped to control the degradation of the alloy. The weight loss measurements of the samples from the immersion tests were also in good agreement with the electrochemical test results. Hence, the results demonstrate the promising role of grain refinement by friction stir processing in tailoring WE43 magnesium alloy with better degradation behavior for temporary bone implant applications. [ABSTRACT FROM AUTHOR]

Microbial-induced carbonate precipitation (MICP) is a promising process with applications in various industries, including soil improvement, bioremediation, and concrete repair. However, comprehensive bibliometric analyses focusing on MICP research in hydrodynamics are lacking. This study analyses 1098 articles from the Scopus database (1999–2024) using VOSviewer and R Studio, identifying information on publications, citations, authors, countries, journals, keyword hotspots, and research terms. Global participation from 66 countries is noted, with China and the United States leading in terms of contributions. The top-cited papers discuss the utilisation of ureolytic microorganisms to enhance soil properties, MICP mechanisms, concrete deterioration mitigation, soil and groundwater flow enhancement, biomineral distribution, and MICP treatment effects on soil hydraulic properties under varying conditions. Keywords like calcium carbonate, permeability, and Sporosarcina pasteurii are pivotal in MICP research. The co-occurrence analysis reveals thematic clusters like microbial cementation and geological properties, advancing our understanding of MICP's interdisciplinary nature and its role in addressing environmental challenges. [ABSTRACT FROM AUTHOR]

To explore the effects of the introduction order of calcium sources and the bacteria-to-calcium ratio on the microbially induced calcium carbonate precipitation (MICP) product CaCO3 and to achieve the regulation of CaCO3 crystal morphology, the mineralisation products of MICP were compared after combining bacteria and calcium at ratios of 1/9, 2/9, 3/9, 4/9, 5/9, and 6/9. A bacterial solution was combined with a urea solution in two calcium addition modes: calcium-first and calcium-later modes. Finally, under the calcium-first addition method, the output of high-purity vaterite-type CaCO3 was achieved at bacteria-to-calcium ratios of 2/9 and 3/9; under the calcium-later addition method, the output of calcite-type CaCO3 could be stabilised, and the change in the bacteria-to-calcium ratio did not have much effect on its crystalline shape. [ABSTRACT FROM AUTHOR]

Precipitation of marine biogenic CaCO 3 minerals occurs at specialist sites, typically with elevated pH and dissolved inorganic carbon, and in the presence of biomolecules which control the nucleation, growth, and morphology of the calcium carbonate structure. Here we explore aragonite precipitation in vitro under conditions inferred to occur in tropical coral calcification media under present and future atmospheric CO 2 scenarios. We vary pH, Ω Ar and pCO 2 between experiments to explore how both HCO 3 − and CO 3 2− influence precipitation rate and we identify the effects of the three most common amino acids in coral skeletons (aspartic acid, glutamic acid and glycine) on precipitation rate and aragonite morphology. We find that fluid Ω Ar or [CO 3 2−] is the main control on precipitation rate at 25 °C, with no significant contribution from HCO 3 − or pH. All amino acids inhibit aragonite precipitation at 0.2–5 mM and the degree of inhibition is inversely correlated with Ω Ar and, in the case of aspartic acid, also inversely correlated with seawater temperature. Aspartic acid inhibits precipitation the most, of the tested amino acids (and generates changes in aragonite morphology) and glycine inhibits precipitation the least. Previous work shows that ocean acidification increases the amino acid content of coral skeletons and probably reduces calcification media Ω Ar , both of which can inhibit aragonite precipitation. This study and previous work shows aragonite precipitation rate is exponentially related to temperature from 10 to 30 °C and small anthropogenic increases in seawater temperature will likely offset the inhibition in precipitation rate predicted to occur due to increased skeletal aspartic acid and reduced calcification media Ω Ar under ocean acidification. [ABSTRACT FROM AUTHOR]

The calcifying cells of corals are responsible for skeleton formation, a process that is the basis for reef building. Their cell biology is therefore of primary interest, but current knowledge is limited because direct in vivo investigation of this cell type is challenging. Studies at the growing edge of laterally extending coral colonies allow for direct observations of actively calcifying cells in living samples. In the current study, we used this approach to study lipid droplets, which are considered storage organelles that fuel cells for physiological processes. Using the fluorescent lipid probe Nile Red and in vivo confocal microscopy, we observed lipid droplets in calcifying cells of the coral Stylophora pistillata and we suggest that they play a key role in coral calcification. [ABSTRACT FROM AUTHOR]

FurongianâTremadocian phosphorites of Estonia are sandstone rich in biogenic apatite, represented by brachiopod detritus. The study focuses on the mineralogical and micro-analytical characterisation of phosphorites from the Aseri, Toolse, and Kabala deposits based on FE-SEM and EPMA analyses. The shell fragments are composed of alternating compact and porous laminae, but with considerably poor preservation of pristine textures, superseded by the formation of authigenic CAF-apatite during the early diagenesis. In all settings, the shells showed preferential uptake of Sr into the porous cryptocrystalline laminae. The altered areas are composed of massive apatite crystallites with Mn-enriched layers. They are frequently covered with pyrite, indicating progressive recrystallisation under the influence of interstitial fluids and fluctuations in redox gradients in coastal environments.

The alveolar bone is a unique type of bone, and the goal of bone tissue engineering (BTE) is to develop methods to facilitate its regeneration. Currently, an emerging trend involves the fabrication of polycaprolactone (PCL)-based scaffolds using a three-dimensional (3D) printing technique to enhance an osteoconductive architecture. These scaffolds are further modified with hydroxyapatite (HA), type I collagen (CGI), or chitosan (CS) to impart high osteoinductive potential. In conjunction with cell therapy, these scaffolds may serve as an appealing alternative to bone autografts. This review discusses research gaps in the designing of 3D-printed PCL-based scaffolds from a biomimetic perspective. The article begins with a systematic analysis of biological mineralisation (biomineralisation) and ossification to optimise the scaffold's structural, mechanical, degradation, and surface properties. This scaffold-designing strategy lays the groundwork for developing a research pathway that spans fundamental principles such as molecular dynamics (MD) simulations and fabrication techniques. Ultimately, this paves the way for systematic in vitro and in vivo studies, leading to potential clinical applications. [ABSTRACT FROM AUTHOR]

Biomineralisation is the process by which living organisms produce hard structures such as shells and bone. There are multiple independent origins of biomineralised skeletons across the tree of life. This review gives a glimpse into the diversity of spiralian biominerals and what they can teach us about the evolution of novelty. It discusses different levels of biological organisation that may be informative to understand the evolution of biomineralisation and considers the relationship between skeletal and non-skeletal biominerals. More specifically, this review explores if cell type and gene regulatory network approaches could enhance our understanding of the evolutionary origins of biomineralisation. [ABSTRACT FROM AUTHOR]

Dolomite (CaMg(CO3)2) precipitation is kinetically inhibited at surface temperatures and pressures. Experimental studies have demonstrated that microbial extracellular polymeric substances (EPS) as well as certain clay minerals may catalyse dolomite precipitation. However, the combined association of EPS with clay minerals and dolomite and their occurrence in the natural environment are not well documented. We investigated the mineral and textural associations within groundwater dolocrete profiles from arid northwest Australia. Microbial EPS is a site of nucleation for both dolomite and authigenic clay minerals in this Late Miocene to Pliocene dolocrete. Dolomite crystals are commonly encased in EPS alveolar structures, which have been mineralised by various clay minerals, including montmorillonite, trioctahedral smectite and palygorskite‐sepiolite. Observations of microbial microstructures and their association with minerals resemble textures documented in various lacustrine and marine microbialites, indicating that similar mineralisation processes may have occurred to form these dolocretes. EPS may attract and bind cations that concentrate to form the initial particles for mineral nucleation. The dolomite developed as nanocrystals, likely via a disordered precursor, which coalesced to form larger micritic crystal aggregates and rhombic crystals. Spheroidal dolomite textures, commonly with hollow cores, are also present and may reflect the mineralisation of a biofilm surrounding coccoid bacterial cells. Dolomite formation within an Mg‐clay matrix is also observed, more commonly within a shallow pedogenic horizon. The ability of the negatively charged surfaces of clay and EPS to bind and dewater Mg2+, as well as the slow diffusion of ions through a viscous clay or EPS matrix, may promote the incorporation of Mg2+ into the mineral and overcome the kinetic effects to allow disordered dolomite nucleation and its later growth. The results of this study show that the precipitation of clay and carbonate minerals in alkaline environments may be closely associated and can develop from the same initial amorphous Ca–Mg–Si‐rich matrix within EPS. The abundance of EPS preserved within the profiles is evidence of past microbial activity. Local fluctuations in chemistry, such as small increases in alkalinity, associated with the degradation of EPS or microbial activity, were likely important for both clay and dolomite formation. Groundwater environments may be important and hitherto understudied settings for microbially influenced mineralisation and for low‐temperature dolomite precipitation. [ABSTRACT FROM AUTHOR]

Microbial-induced carbonate precipitation (MICP) is a promising process with applications in various industries, including soil improvement, bioremediation, and concrete repair. However, comprehensive bibliometric analyses focusing on MICP research in hydrodynamics are lacking. This study analyses 1098 articles from the Scopus database (1999–2024) using VOSviewer and R Studio, identifying information on publications, citations, authors, countries, journals, keyword hotspots, and research terms. Global participation from 66 countries is noted, with China and the United States leading in terms of contributions. The top-cited papers discuss the utilisation of ureolytic microorganisms to enhance soil properties, MICP mechanisms, concrete deterioration mitigation, soil and groundwater flow enhancement, biomineral distribution, and MICP treatment effects on soil hydraulic properties under varying conditions. Keywords like calcium carbonate, permeability, and Sporosarcina pasteurii are pivotal in MICP research. The co-occurrence analysis reveals thematic clusters like microbial cementation and geological properties, advancing our understanding of MICP’s interdisciplinary nature and its role in addressing environmental challenges.

Coral skeletal boron geochemistry offers opportunities to probe the pH of the calcification media (pH CM) of modern and fossil specimens, to estimate past changes in seawater pH and to explore the biomineralisation response to future ocean acidification. In this research we grew 2 Stylophora pistillata coral microcolonies over glass coverslips to allow analysis of the pH sensitive dye SNARF-1, in the extracellular calcification medium at the growing edge of colonies where the first aragonite crystals are formed, under both light and dark conditions. We use secondary ion mass spectrometry (SIMS) to measure the boron isotopic composition (δ11B) of the skeleton close to the growth edge after 2 to 3 days of additional calcification had enlarged the crystals until they joined, generating a continuous sheet of aragonite. Mean skeletal δ11B-pH CM estimates are higher than those by SNARF-1 by 0.35–0.44 pH units. These differences either reflect real variations in the pH of the calcification media associated with each measurement technique or indicate other changes in the biomineralisation process which influence skeletal δ11B. SNARF-1 measures directly the pH of the extracellular calcification medium while skeletal δ11B analyses aragonite potentially formed via both extracellular and intracellular biomineralisation pathways. Analysis of a third coral specimen, also growing on a glass slide but with a 5 cm long branch, indicated good agreement between the δ11B value of the apex of the branch and the skeletal growth edge. The tissues overlying both these regions were transparent indicating they had low symbiont densities. This suggests that the biomineralisation process is broadly comparable between these sites and that studies growing corals over glass slides/coverslips provide representative data for the colony apex. [ABSTRACT FROM AUTHOR]

Haima cold seep ecosystem is on the northwestern slope of the South China Sea, which is characterised by high pressure, low temperature, hypoxia, and low pH value. The deep-sea mussel Gigantidas haimaensis is distributed in this ecosystem. Previous studies have focused on its adaptation to abiotic stress, biogeography, ecotoxicology, genomes, immunity and symbiosis, but knowledge on biomineralisation remains lacking. Herein, we generated a comprehensive transcript dataset from G. haimaensis mantle tissue, and 30255 unigenes were assembled. The top 20 most highly expressed genes are related to energy supply, such as mitochondrial genes, suggesting they may mediate the adaptability of this deep-sea mussel to the high pressure and hypoxia environment. Eleven shell matrix protein (SMP)-related genes were identified from the transcriptome data. Quantitative PCR analyses showed that five of ten acidic SMPs and nacreous-layer-matrix-protein genes (nacrein, perlucin, perlwapin, pif and mantle protein) were highly expressed in mantle tissue, while the expressions of other five genes (chitinase, SPARC, TRY, papilin and calmodulin) were low. Scanning electron microscopy showed that the shell was composed of a prismatic layer and a nacreous layer, and every nacreous layer was made of the whole pieces of aragonite that stacked on top of each other. These results indicated the conservation of the structure and functions of nacreous matrix genes in G. haimaensis. Moreover, the nacreous layer was made of whole pieces of aragonite that were not quadrilateral or polygonal pieces. Studying these genes will likely reveal the molecular mechanisms of biomineralisation in G. haimaensis and other deep-sea mussels. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) has provoked changes in the carbonate saturation state that may alter the formation and structural biomineralisation of calcium carbonate exoskeletons for marine organisms. Biomineral production in organisms such as cold-water corals (CWC) rely on available carbonate in the water column and the ability of the organism to sequester ions from seawater or nutrients for the formation and growth of a skeletal structure. As an important habitat structuring species, it is essential to examine the impact that anthropogenic stressors (i.e., OA and rising seawater temperatures) have on living corals and the structural properties of dead coral skeletons; these are important contributors to the entire reef structure and the stability of CWC mounds. In this study, dead coral skeletons in seawater were exposed to various levels of pCO2 and different temperatures over a 12-month period. Nanoindentation was subsequently conducted to assess the structural properties of coral samples’ elasticity (E) and hardness (H), whereas the amount of dissolution was assessed through scanning electron microscopy. Overall, CWC samples exposed to elevated pCO2 and temperature show changes in properties which leave them more susceptible to breakage and may in turn negatively impact the formation and stability of CWC mound development.

Abstract The aim of this study is to identify the biomineralisation processes in hot springs of North‐West Euboea Island by assessing the physico‐chemical parameters of the hot water, the travertine mineralogical composition and facies, and the cyanobacterial microflora. In the studied area, the main mineral phases are calcite and aragonite, creating laminated and shrub facies of travertine deposits in close association with the cyanobacterial microflora. Microscopic analysis of fresh and cultured field samples shows the presence of 81 taxa of Cyanobacteria belonging to six orders, that is, Oscillatoriales, Synechococcales, Spirulinales, Chroococcales, Nostocales and Chroococcidiopsidales with the main factors controlling biodiversity being temperature, salinity and access to sunlight. No Cyanobacteria species were identified in areas with temperatures over 65oC. In areas with high salinity (27–37‰), the order Oscillatoriales predominates. On the other hand, in areas with high temperatures (63oC), fewer orders were observed, usually only Synechococcales and Spirulinales. In areas with lower temperatures (37oC), larger numbers of Cyanobacteria orders were identified. Additionally, salinity seems to regulate the presence of the Nostocales order. The combined geobiological study revealed the presence of four biomineralisation processes involving calcium carbonate minerals, that is, (i) filamentous Cyanobacteria and extracellular polymeric substances trapping calcium carbonate crystals, (ii) extracellular polymeric substances acting as a template favouring mineral precipitation for crystal nucleation, (iii) formation of calcified Cyanobacteria sheaths and (iv) alteration of calcium carbonate crystals by endolithic Cyanobacteria. The identified biomineralisation processes suggest that the formation of calcium carbonate crystals is due to the metabolic activity of Cyanobacteria, or that the Cyanobacteria favour the deposition or the alteration of already existing crystals. The combination of these processes and the non‐biotic (abiotic) mineralisation result in the formation of hybrid carbonates in the study area.

Abstract Cyanobacteria are considered to be among the first microorganisms to settle in hot springs where they form a favourable environment for further biological establishment. Nevertheless, the exact pioneer species and how early they start participating in the biomineralisation processes remain unknown. The aim of the present study was twofold, that is, to identify the pioneer Cyanobacteria in hot springs (i.e. Aedipsos area, Greece) and to record their early biomineralisation processes. The in situ experimental approach included the setup of sterile glass and/or plexiglass slides in several locations to facilitate colonisation by Cyanobacteria, and removal of slides for study after 48–202 h. Synechococcales (37%) and Oscillatoriales (33%) were the dominant orders, followed by Chroococcales (15%) and Spirulinales (11%); whereas Chroococcidiopsidales (4%) was found only in a few sites. The order Nostocales was not observed at the early stages of colonisation although it was present in mature stages. Forty‐three species of Cyanobacteria were identified as pioneer microorganisms, with Spirulina subtilissima being the most frequently found. The most common pioneers were multicellular filamentous Cyanobacteria, that is, organisms with a large surface area able to form significant amounts of extracellular polymeric substances. Among the pioneers, thermophilic species of Cyanobacteria were typical such as Chroococcidiopsis thermalis, Chroococcus thermalis, Leptolyngbya thermalis, S. subtilissima and Symploca thermalis, as well as typical limestone substrate species such as Chroococcus lithophilus and Leptolyngbya laminosa. Temperature seems to affect biodiversity. Also, pioneers were found to contribute to the biomineralisation processes from their first appearance. In the studied samples, three biomineralisation processes were identified, that is, (i) calcification of cyanobacterial sheaths, (ii) trapping of carbonate crystals on a crystal retention lattice formed by extracellular polymeric substances and filaments and (iii) trapping and confinement of carbonate crystals around filamentous Cyanobacteria.

Porous wollastonite ceramic was successfully prepared via a wet milling method using calcium oxide (CaO) and silicon dioxide (SiO 2) as the raw materials, and a gel casting method using potato starch as the pore-forming agent. X-ray diffraction results demonstrated that a single phase of β-wollastonite was obtained at 1050 and 1150 °C. Meanwhile, a single phase of pseudo-wollastonite was obtained at 1250 °C. The increasing sintering temperature has significantly affected the phase, microstructure, linear shrinkage, density, porosity, and compressive strength of the porous wollastonite ceramics. When the sintering temperature was increased, the density and compressive strength of wollastonite ceramics were increased. However, its pore size was decreased with increasing sintering temperature, i.e., the pore size of the sample sintered at 850 °C was 400–500 μm, which was reduced to 300–400 μm after the sample was sintered at 1250 °C. The surface of all porous ceramic samples exhibited apatite formation within a day. Thus, single-phase porous wollastonite ceramics, with good porosity and strength, were successfully fabricated using the gel casting method. [ABSTRACT FROM AUTHOR]

Lipids may serve as energy reserves to support coral calcification, allow acclimation to higher temperatures, and are implicated in the control of CaCO3 precipitation. Here, we report the lipid composition of the soft tissues (including host and symbionts) of 7 massive Porites spp. coral colonies (4 × P. lutea and 3 × P. murrayensis), which were cultured under different pCO2 concentrations (180, 260, 400 and 750 µatm) and at two temperatures (25 ℃ and 28 ℃), below the thermal stress threshold. We report the fatty acid methyl esters (FAME), free fatty acid (FFA) to total fatty acid content, sterol and wax ester profiles, and identify two ketones (n-alkanone) and three long chain aldehyde (n-alkanal) derivatives. Increasing seawater temperature significantly increases the contributions of FFAs to the total lipids, of C18:2 and C20:0 to the total FFA pool, of C14:0 to total FAME, and of campesterol to total sterol. The temperature increase also reduces the contributions of unusual fatty acid derivatives to total lipids, of C14:0, C15:0, C16:0 and C17:0 saturated free fatty acids to total FFAs, and of C16:0 FA to total FAME. Fatty acids are implicated in the control of membrane structure fluidity and the observed changes may promote acclimation and thermostability as temperature varies. Seawater pCO2 has no significant effect on the composition of tissue lipids with the exception that the contribution of C14:0 FA to total lipid content is significantly lower at 180 µatm compared to 260 and 750 µatm. Decreased contribution of total sterols and unusual fatty acid derivatives and increased contribution of total FFAs to total lipids are observed in the fastest calcifying coral (a P. lutea specimen) compared to the other corals, under all pCO2 and temperature conditions. Although a rapid calcifier this genotype has been shown previously to exhibit pronounced abnormal changes in skeletal morphology in response to decreased seawater pCO2. Variations in tissue lipid composition between coral genotypes may influence their resilience to future climate change. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) has provoked changes in the carbonate saturation state that may alter the formation and structural biomineralisation of calcium carbonate exoskeletons for marine organisms. Biomineral production in organisms such as cold-water corals (CWC) rely on available carbonate in the water column and the ability of the organism to sequester ions from seawater or nutrients for the formation and growth of a skeletal structure. As an important habitat structuring species, it is essential to examine the impact that anthropogenic stressors (i.e., OA and rising seawater temperatures) have on living corals and the structural properties of dead coral skeletons; these are important contributors to the entire reef structure and the stability of CWC mounds. In this study, dead coral skeletons in seawater were exposed to various levels of pCO2 and different temperatures over a 12-month period. Nanoindentation was subsequently conducted to assess the structural properties of coral samples' elasticity (E) and hardness (H), whereas the amount of dissolution was assessed through scanning electron microscopy. Overall, CWC samples exposed to elevated pCO2 and temperature show changes in properties which leave them more susceptible to breakage and may in turn negatively impact the formation and stability of CWC mound development. [ABSTRACT FROM AUTHOR]

Furongian–Tremadocian phosphorites of Estonia are sandstone rich in biogenic apatite, represented by brachiopod detritus. The study focuses on the mineralogical and micro-analytical characterisation of phosphorites from the Aseri, Toolse, and Kabala deposits based on FE-SEM and EPMA analyses. The shell fragments are composed of alternating compact and porous laminae, but with considerably poor preservation of pristine textures, superseded by the formation of authigenic CAF-apatite during the early diagenesis. In all settings, the shells showed preferential uptake of Sr into the porous cryptocrystalline laminae. The altered areas are composed of massive apatite crystallites with Mn-enriched layers. They are frequently covered with pyrite, indicating progressive recrystallisation under the influence of interstitial fluids and fluctuations in redox gradients in coastal environments. [ABSTRACT FROM AUTHOR]

Byronids are problematic fossils of possible cnidarian affinity, only rarely reported from the Devonian, but never previously studied in the Barrandian area, Czech Republic. Two new species Prestephanoscyphus branzovensis sp. nov. and Prestephanoscyphus robustus sp. nov. are erected from the Lochkovian and the Eifelian, respectively. Four poorly known species referred to Byronia are described in open nomenclature from the Emsian and Eifelian. The new genus Parabyronia gen. nov. with the type species Parabyronia elegans sp. nov. is closely related to other sphenothallids but is distinguished by transverse ridges on its theca and short spines at the apertural end of the theca. Definite identification of phosphatic rings as the attachment structure of byronids was proved by new material of the Lochkovian age. A dwarf conularia Pidiconularia gen. nov. with the type species Pidiconularia tubulata sp. nov. is remarkable by its minute size and very fine ornament; its conulariid affinity is proved by subrectangular cross-section and four internal carinae. Microstructure of theca of Prestephanoscyphus is characterised by alternation of compact laminae of aligned columnar microcrystallites and chambered laminae with isometric microcrystallites of apatite. Accretionary growth of byronid theca and structure of the holdfast with basal opening for the adhesive pedal disc support their cnidarian affinity although they likely display the bilateral instead of tetramerous symmetry. The protective function of bilaterally symmetrical whorls of internal apophyses in Prestephanoscyphus is suggested and their role in strengthening of thecal wall or supporting function of gastric septa are disputed. The byronids are regarded as epibionts rather than attached to the rocks. They are representatives of benthic groups with phosphatic shells that declined with decreasing availability of phosphorus in seas and oceans. [ABSTRACT FROM AUTHOR]

Cyanobacteria are considered to be among the first microorganisms to settle in hot springs where they form a favourable environment for further biological establishment. Nevertheless, the exact pioneer species and how early they start participating in the biomineralisation processes remain unknown. The aim of the present study was twofold, that is, to identify the pioneer Cyanobacteria in hot springs (i.e. Aedipsos area, Greece) and to record their early biomineralisation processes. The in situ experimental approach included the setup of sterile glass and/or plexiglass slides in several locations to facilitate colonisation by Cyanobacteria, and removal of slides for study after 48–202 h. Synechococcales (37%) and Oscillatoriales (33%) were the dominant orders, followed by Chroococcales (15%) and Spirulinales (11%); whereas Chroococcidiopsidales (4%) was found only in a few sites. The order Nostocales was not observed at the early stages of colonisation although it was present in mature stages. Forty‐three species of Cyanobacteria were identified as pioneer microorganisms, with Spirulina subtilissima being the most frequently found. The most common pioneers were multicellular filamentous Cyanobacteria, that is, organisms with a large surface area able to form significant amounts of extracellular polymeric substances. Among the pioneers, thermophilic species of Cyanobacteria were typical such as Chroococcidiopsis thermalis, Chroococcus thermalis, Leptolyngbya thermalis, S. subtilissima and Symploca thermalis, as well as typical limestone substrate species such as Chroococcus lithophilus and Leptolyngbya laminosa. Temperature seems to affect biodiversity. Also, pioneers were found to contribute to the biomineralisation processes from their first appearance. In the studied samples, three biomineralisation processes were identified, that is, (i) calcification of cyanobacterial sheaths, (ii) trapping of carbonate crystals on a crystal retention lattice formed by extracellular polymeric substances and filaments and (iii) trapping and confinement of carbonate crystals around filamentous Cyanobacteria. [ABSTRACT FROM AUTHOR]

The aim of this study is to identify the biomineralisation processes in hot springs of North‐West Euboea Island by assessing the physico‐chemical parameters of the hot water, the travertine mineralogical composition and facies, and the cyanobacterial microflora. In the studied area, the main mineral phases are calcite and aragonite, creating laminated and shrub facies of travertine deposits in close association with the cyanobacterial microflora. Microscopic analysis of fresh and cultured field samples shows the presence of 81 taxa of Cyanobacteria belonging to six orders, that is, Oscillatoriales, Synechococcales, Spirulinales, Chroococcales, Nostocales and Chroococcidiopsidales with the main factors controlling biodiversity being temperature, salinity and access to sunlight. No Cyanobacteria species were identified in areas with temperatures over 65oC. In areas with high salinity (27–37‰), the order Oscillatoriales predominates. On the other hand, in areas with high temperatures (63oC), fewer orders were observed, usually only Synechococcales and Spirulinales. In areas with lower temperatures (37oC), larger numbers of Cyanobacteria orders were identified. Additionally, salinity seems to regulate the presence of the Nostocales order. The combined geobiological study revealed the presence of four biomineralisation processes involving calcium carbonate minerals, that is, (i) filamentous Cyanobacteria and extracellular polymeric substances trapping calcium carbonate crystals, (ii) extracellular polymeric substances acting as a template favouring mineral precipitation for crystal nucleation, (iii) formation of calcified Cyanobacteria sheaths and (iv) alteration of calcium carbonate crystals by endolithic Cyanobacteria. The identified biomineralisation processes suggest that the formation of calcium carbonate crystals is due to the metabolic activity of Cyanobacteria, or that the Cyanobacteria favour the deposition or the alteration of already existing crystals. The combination of these processes and the non‐biotic (abiotic) mineralisation result in the formation of hybrid carbonates in the study area. [ABSTRACT FROM AUTHOR]

Abstract Background Microbially induced calcite precipitation (MICP) is an ancient property of bacteria, which has recently gained considerable attention for biotechnological applications. It occurs as a by-product of bacterial metabolism and involves a combination of chemical changes in the extracellular environment, e.g. pH increase, and presence of nucleation sites on the cell surface or extracellular substances produced by the bacteria. However, the molecular mechanisms underpinning MICP and the interplay between the contributing factors remain poorly understood, thus placing barriers to the full biotechnological and synthetic biology exploitation of bacterial biomineralisation. Results In this study, we adopted a bottom-up approach of systematically engineering Bacillus subtilis, which has no detectable intrinsic MICP activity, for biomineralisation. We showed that heterologous production of urease can induce MICP by local increases in extracellular pH, and this can be enhanced by co-expression of urease accessory genes for urea and nickel uptake, depending on environmental conditions. MICP can be strongly enhanced by biofilm-promoting conditions, which appeared to be mainly driven by production of exopolysaccharide, while the protein component of the biofilm matrix was dispensable. Attempts to modulate the cell surface charge of B. subtilis had surprisingly minor effects, and our results suggest this organism may intrinsically have a very negative cell surface, potentially predisposing it for MICP activity. Conclusions Our findings give insights into the molecular mechanisms driving MICP in an application-relevant chassis organism and the genetic elements that can be used to engineer de novo or enhanced biomineralisation. This study also highlights mutual influences between the genetic drivers and the chemical composition of the surrounding environment in determining the speed, spatial distribution and resulting mineral crystals of MICP. Taken together, these data pave the way for future rational design of synthetic precipitator strains optimised for specific applications.

Plastic pollution in water ecosystems is threatening the survival of wildlife. In particular, microplastics may be encapsulated into calcium carbonate, a crucial building block of hard tissue in many species such as molluscs, corals, phytoplankton, sponges, echinoderms, and crustaceans. Actually little is known on the effect of humic acids, a common component of dissolved organic matter, on the encapsulation of microplastic into calcium carbonate. Here, we precipitated calcium carbonate with humic acids and polystyrene microspheres. The precipitation process was followed by measuring pH during the reaction. Composition, structure, morphology, surface properties and microspheres encapsulation extent were analysed by infrared spectroscopy, X-ray powder diffraction, atomic force microscopy, scanning electron microscopy, total organic carbon analysis, thermogravimetric analysis, nuclear magnetic resonance spectroscopy, electrophoretic and dynamic light scattering. Results show, for the first time, that encapsulation of polystyrene microspheres into calcite crystals occurs only after the treatment of the microspheres with humic acids, leading to encapsulation of about 5% of the initial microspheres mass. On the contrary, untreated microspheres did not encapsulate in calcium carbonate. Our findings imply that exposure of microplastics to dissolved organic matter in water ecosystems could result in enhanced encapsulation into the exoskeleton and endoskeleton of aquatic organisms. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity represents an important first-line organism response to newly introduced or changing environmental constraints. Knowledge about structural responses to environmental stressors could thus be an essential measure to predict species and ecosystem responses to a world in change. In this study, we combined morphometric analyses with environmental modelling to identify direct shape responses of the predatory gastropod Nucella lapillus to large-scale variability in sea surface temperature and the carbonate system. Our models suggest that the state of the carbonate system and, more specifically, the substrate inhibitor ratio ([HCO3−][H+]−1) (SIR) has a dominant effect on the shell shape of this intertidal muricid. Populations in regions with a lower SIR tend to form narrower shells with a higher spire to body whorl ratio, whereas populations in areas with a higher SIR form wider shells with a much lower spire to body whorl ratio. These results indicate that a widespread phenotypic response of N. lapillus to continuing ocean acidification can be expected, potentially altering the phenotypic response pattern to predator or wave exposure regimes with profound implications for North Atlantic rocky shore communities.

• 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]

Popularly known as "chalky teeth", molar hypomineralisation (MH) affects over 1-in-5 children worldwide, triggering massive amounts of suffering from toothache and rapid decay. MH stems from childhood illness and so offers a medical-prevention avenue for improving oral and paediatric health. With a cross-sector translational research and education network (The D3 Group; thed3group.org ) now highlighting this global health opportunity, aetiological understanding is urgently needed to enable better awareness, management and eventual prevention of MH. Causation and pathogenesis of "chalky enamel spots" (i.e., demarcated opacities, the defining pathology of MH) remain unclear despite 100 years of investigation. However, recent biochemical studies provided a pathomechanistic breakthrough by explaining several hallmarks of chalky opacities for the first time. This article outlines these findings in context of previous understanding and provides a working model for future investigations. The proposed pathomechanism, termed "mineralisation poisoning", involves localised exposure of immature enamel to serum albumin. Albumin binds to enamel-mineral crystals and blocks their growth, leading to chalky opacities with distinct borders. Being centred on extracellular fluid rather than enamel-forming cells as held by dogma, this localising pathomechanism invokes a new type of connection with childhood illness. These advances open a novel direction for research into pathogenesis and causation of MH, and offer prospects for better clinical management. Future research will require wide-ranging inputs that ideally should be coordinated through a worldwide translational network. We hope this breakthrough will ultimately lead to medical prevention of MH, prompting global health benefits including major reductions in childhood tooth decay. [ABSTRACT FROM AUTHOR]

Aim of the study was to investigate the atherosclerotic calcification employing our original technique of tissue staining, embedding, and backscattered scanning electron microscopy. Materials and methods. Atherosclerotic plaques excised during the carotid endarterectomy have been fixed in 10 % neutral phosphate buffered saline formalin for 24 hours, stained in 2 % osmium tetroxide for 60 hours and in alcoholic uranyl acetate for 5 hours with the subsequent epoxy resin embedding, grinding, polishing, lead citrate counterstaining for 7 minutes, sputter coating with carbon and backscattered scanning electron microscopy. We then analysed localisation, structure, and microenvironment of the calcium deposits. Results. Within the atherosclerotic plaques, we identified 3 distinct calcification morphologies: compact homogenous macrocalcifications, sheet-like heterogeneous macrocalcifications along the destructed collagen and elastin fibers, and microcalcifications around large calcium deposits with the sharp margins. However, even relatively homogenous compact macrocalcifications had uneven distribution of electron density. In conjunction with groups of mineral deposits of distinct calcium phosphate phases including nascent calcified loci, this testified to ongoing calcium phosphate maturation while multiple microcalcifications merging into the single macrocalcification indicated ossification. Compact ossifying macrocalcifications with smooth margins frequently had a dense connective tissue capsule. The microenvironment of calcium deposits was often characterised by leaky neovessels. Conclusion. Diversity of calcification morphologies and ossification in atherosclerotic plaques is similar to those observed in calcific aortic valve disease and bioprosthetic heart valve failure. Combined with atherosclerotic plaque disaggregation followed by flow cytometry and singlecell RNA sequencing, our technique may improve our understanding of atherosclerotic calcification and lead to the identification of appropriate therapeutic targets to prevent or retard this process.

Significant interest has been inspired by the exceptional biological performance of akermanite bioceramic in tissue engineering. This exertion investigates effect of fuel on the biomineralisation using three different fuels viz., glycine, L-alanine, and urea. The materials were prepared through sol-gel combustion method by using Glycine, L Alanine and Urea as a fuel and encoded as AK-G, AK-AL, and AK-U. The mechanism associated in the synthesis of these bioceramic was examined by thermal analysis. The pure phase achieved at 900 °C was confirmed by powder XRD, the functional groups were identified by FTIR analysis. When glycine was employed as the fuel, the average crystallite size formed was 32–36 nm; however, for alanine and urea, shows increase in value of 34–40 and 37–43 nm, respectively. Surface morphology and elemental composition were confirmed by SEM/EDX. AFM analysis indicates that Glycine imparts higher surface roughness than other ceramic materials, which promotes nucleation of hydroxyapatite during biomineralization. Among the three samples, AK-Glycine exhibits considerable improvements in bioactivity with a Ca/P ratio of 1.60 which is closer to natural hydroxyapatite (1.67) and makes it an appropriate candidate for bone tissue engineering applications.

Background: Microbially induced calcite precipitation (MICP) is an ancient property of bacteria, which has recently gained considerable attention for biotechnological applications. It occurs as a by-product of bacterial metabolism and involves a combination of chemical changes in the extracellular environment, e.g. pH increase, and presence of nucleation sites on the cell surface or extracellular substances produced by the bacteria. However, the molecular mechanisms underpinning MICP and the interplay between the contributing factors remain poorly understood, thus placing barriers to the full biotechnological and synthetic biology exploitation of bacterial biomineralisation. Results: In this study, we adopted a bottom-up approach of systematically engineering Bacillus subtilis, which has no detectable intrinsic MICP activity, for biomineralisation. We showed that heterologous production of urease can induce MICP by local increases in extracellular pH, and this can be enhanced by co-expression of urease accessory genes for urea and nickel uptake, depending on environmental conditions. MICP can be strongly enhanced by biofilm-promoting conditions, which appeared to be mainly driven by production of exopolysaccharide, while the protein component of the biofilm matrix was dispensable. Attempts to modulate the cell surface charge of B. subtilis had surprisingly minor effects, and our results suggest this organism may intrinsically have a very negative cell surface, potentially predisposing it for MICP activity. Conclusions: Our findings give insights into the molecular mechanisms driving MICP in an application-relevant chassis organism and the genetic elements that can be used to engineer de novo or enhanced biomineralisation. This study also highlights mutual influences between the genetic drivers and the chemical composition of the surrounding environment in determining the speed, spatial distribution and resulting mineral crystals of MICP. Taken together, these data pave the way for future rational design of synthetic precipitator strains optimised for specific applications. [ABSTRACT FROM AUTHOR]