Literatura académica sobre el tema "Biologically-Controlled biomineralization"
Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros
Consulte las listas temáticas de artículos, libros, tesis, actas de conferencias y otras fuentes académicas sobre el tema "Biologically-Controlled biomineralization".
Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.
También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.
Artículos de revistas sobre el tema "Biologically-Controlled biomineralization"
1
Ehrlich, Hermann, Elizabeth Bailey, Marcin Wysokowski y Teofil Jesionowski. "Forced Biomineralization: A Review". Biomimetics 6, n.º 3 (12 de julio de 2021): 46. http://dx.doi.org/10.3390/biomimetics6030046.
Texto completoResumen
Biologically induced and controlled mineralization of metals promotes the development of protective structures to shield cells from thermal, chemical, and ultraviolet stresses. Metal biomineralization is widely considered to have been relevant for the survival of life in the environmental conditions of ancient terrestrial oceans. Similar behavior is seen among extremophilic biomineralizers today, which have evolved to inhabit a variety of industrial aqueous environments with elevated metal concentrations. As an example of extreme biomineralization, we introduce the category of “forced biomineralization”, which we use to refer to the biologically mediated sequestration of dissolved metals and metalloids into minerals. We discuss forced mineralization as it is known to be carried out by a variety of organisms, including polyextremophiles in a range of psychrophilic, thermophilic, anaerobic, alkaliphilic, acidophilic, and halophilic conditions, as well as in environments with very high or toxic metal ion concentrations. While much additional work lies ahead to characterize the various pathways by which these biominerals form, forced biomineralization has been shown to provide insights for the progression of extreme biomimetics, allowing for promising new forays into creating the next generation of composites using organic-templating approaches under biologically extreme laboratory conditions relevant to a wide range of industrial conditions.
2
Pamirsky, Igor E. y Kirill S. Golokhvast. "Origin and Status of Homologous Proteins of Biomineralization (Biosilicification) in the Taxonomy of Phylogenetic Domains". BioMed Research International 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/397278.
Texto completoResumen
The taxonomic affiliation (in the systematisation of viruses, and biological domains) of known peptides and proteins of biomineralization (silicateins, silaffins, silacidins and silicase) and their primary structure homologues were analyzed (methodsin silico; using Uniprot database). The total number of known peptides and proteins of biosilicification was counted. The data of the quantitative distribution of the detected homologues found in nature are presented. The similarity of the primary structures of silaffins, silacidins, silicateins, silicase, and their homologues was 21–94%, 45–98%, 39–50%, and 28–40%, respectively. These homologues are found in many organisms, from the Protista to the higher plants and animals, including humans, as well as in bacteria and extracellular agents, and they perform a variety of biological functions, such as biologically controlled mineralisation. The provisional classification of these biomineralization proteins is presented. The interrelation of the origin of the first organic polymers and biomineralization is discussed.
3
Okada, Satoshi, Chong Chen, Tomo-o. Watsuji, Manabu Nishizawa, Yohey Suzuki, Yuji Sano, Dass Bissessur, Shigeru Deguchi y Ken Takai. "The making of natural iron sulfide nanoparticles in a hot vent snail". Proceedings of the National Academy of Sciences 116, n.º 41 (24 de septiembre de 2019): 20376–81. http://dx.doi.org/10.1073/pnas.1908533116.
Texto completoResumen
Biomineralization in animals exclusively features oxygen-based minerals with a single exception of the scaly-foot gastropod Chrysomallon squamiferum, the only metazoan with an iron sulfide skeleton. This unique snail inhabits deep-sea hot vents and possesses scales infused with iron sulfide nanoparticles, including pyrite, giving it a characteristic metallic black sheen. Since the scaly-foot is capable of making iron sulfide nanoparticles in its natural habitat at a relatively low temperature (∼15 °C) and in a chemically dynamic vent environment, elucidating its biomineralization pathways is expected to have significant industrial applications for the production of metal chalcogenide nanoparticles. Nevertheless, this biomineralization has remained a mystery for decades since the snail’s discovery, except that it requires the environment to be rich in iron, with a white population lacking in iron sulfide known from a naturally iron-poor locality. Here, we reveal a biologically controlled mineralization mechanism employed by the scaly-foot snail to achieve this nanoparticle biomineralization, through δ34 S measurements and detailed electron-microscopic investigations of both natural scales and scales from the white population artificially incubated in an iron-rich environment. We show that the scaly-foot snail mediates biomineralization in its scales by supplying sulfur through channel-like columns in which reaction with iron ions diffusing inward from the surrounding vent fluid mineralizes iron sulfides.
4
SAKURAI, S., R. ASAKAWA, F. HIROTA, T. SATO, K. SERA y J. ITOH. "QUANTITATIVE AND QUALITATIVE ANALYSIS OF FLUORIDE AND MULTI ELEMENTS OF SHARK TEETH BY PIXE". International Journal of PIXE 18, n.º 03n04 (enero de 2008): 123–29. http://dx.doi.org/10.1142/s0129083508001466.
Texto completoResumen
Biomineralization has two types, biologically induced mineralization (BIM) and biologically controlled mineralization (BCM). Shark teeth is a typical representative of BCM. We have measured concentrations of fluorine and multi elements in shark teeth collected in the south of Japan. As a result, it was confirmed that the sample preparation method, which was established for the biological samples, is applicable to the shark teeth samples and the elemental concentration was obtained in good accuracy and reproducibility. Moreover, we clarified that the shark teeth is composed of Fluorapatite by the combination with X-ray Diffraction. Fluorine concentration is found to be 5500 µg/g in the shark teeth. We have 100 samples of Shark teeth and are planning on reporting the findings of a study with larger samples in the near future.
5
Cuéllar-Cruz, Mayra, Karina Sandra Pérez, María Eugenia Mendoza y Abel Moreno. "Biocrystals in Plants: A Short Review on Biomineralization Processes and the Role of Phototropins into the Uptake of Calcium". Crystals 10, n.º 7 (9 de julio de 2020): 591. http://dx.doi.org/10.3390/cryst10070591.
Texto completoResumen
The biomineralization process is a mechanism inherent to all organisms of the Earth. Throughout the decades, diverse works have reported that the origin of life is tied to crystals, specifically to biominerals of silica that catalyzed RNA, and had some influence in the homochirality. Although the mechanism by which crystals surfaces (minerals) gave origin to life has not yet been proven, the truth is that, up to the present, biominerals are being synthetized by the organisms of different kingdoms in two basic ways: biologically induced and biologically controlled biomineralization. Paradoxically, this fact makes a fundamental difference between inorganic materials and those formed by living organisms, as the latter are associated with macromolecules that are bound to the mineral phase. Conserving growth and formation of these biogenic organic crystals inside cells is a fascinating subject that has been studied mainly in some of the kingdoms, like Monera (bacteria), Fungi (yeasts), and Animalia (Homo sapiens). Notwithstanding in the Plantae kingdom, the formation, conservation, and functions of crystals has not yet been completely elucidated and described, which is of particular relevance because life on Earth, as we know it, would not be possible without plants. The aim of the present work is to revise the different crystals of calcium oxalate synthetized inside the cells of plants, as well as to identify the mechanism of their formation and their possible functions in plants. The last part is related to the existence of certain proteins called phototropins, which not only work as the blue-light sensors, but they also play an important role on the accumulation of calcium in vacuoles. This new trend is shortly reviewed to explain the characteristics and their plausible role in the calcium uptake along with the biomineralization processes.
6
Hoffmann, René, Benjamin J. Linzmeier, Kouki Kitajima, Gernot Nehrke, Martin Dietzel, Niels Jöns, Kevin Stevens y Adrian Immenhauser. "Complex Biomineralization Pathways of the Belemnite Rostrum Cause Biased Paleotemperature Estimates". Minerals 11, n.º 12 (12 de diciembre de 2021): 1406. http://dx.doi.org/10.3390/min11121406.
Texto completoResumen
Paleotemperatures based on δ18O values derived from belemnites are usually “too cold” compared to other archives and paleoclimate models. This temperature bias represents a significant obstacle in paleoceanographic research. Here we show geochemical evidence that belemnite calcite fibers are composed of two distinct low-Mg calcite phases (CP1, CP2). Phase-specific in situ measurement of δ18O values revealed a systematic offset of up to 2‰ (~8 °C), showing a lead–lag signal between both phases in analyses spaced less than 25 µm apart and a total fluctuation of 3.9‰ (~16 °C) within a 2 cm × 2 cm portion of a Megateuthis (Middle Jurassic) rostrum. We explain this geochemical offset and the lead–lag signal for both phases by the complex biomineralization of the belemnite rostrum. The biologically controlled formation of CP1 is approximating isotope fractionation conditions with ambient seawater to be used for temperature calculation. In contrast, CP2 indicates characteristic non-isotope equilibrium with ambient seawater due to its formation via an amorphous Ca-Mg carbonate precursor at high solid-to-liquid ratio, i.e., limited amounts of water were available during its transformation to calcite, thus suggesting lower formation temperatures. CP2 occludes syn vivo the primary pore space left after formation of CP1. Our findings support paleobiological interpretations of belemnites as shelf-dwelling, pelagic predators and call for a reassessment of paleoceanographic reconstructions based on belemnite stable isotope data.
7
Giordani, Paolo, Paolo Modenesi y Mauro Tretiach. "Determinant factors for the formation of the calcium oxalate minerals, weddellite and whewellite, on the surface of foliose lichens". Lichenologist 35, n.º 3 (mayo de 2003): 255–70. http://dx.doi.org/10.1016/s0024-2829(03)00028-8.
Texto completoResumen
AbstractThe factors influencing the predominance of one of the two mineral forms of calcium oxalate (CO), the monohydrated whewellite (COM) and the di-hydrated weddellite (COD), forming the pruina of the upper cortex of lichens, have been investigated through a simple, sensitive histochemical assay: toluidine blue O (TBO), a metachromatic staining test. The differential reactivity of 43 thalli of 17 pruinose foliose species, supplemented by X-ray diffraction analysis and observations with polarizing and scanning electron microscopy, suggests that the histochemical reactivity of hyphal walls and cementing substances of the upper cortex are related to the density of anionic charges. These factors are probably due to the occurrence of polyuronic acid substances that strongly affects the mineralization of CO. Di-hydrated wedellite is always associated with TBO metachromatic reactivity, and COM with orthochromatic reactivity. When the material has an ambiguous ortho/metachromatic reactivity, COD and COM may occur together. This study presents the first experimental evidence that in lichens CO biomineralization is at least partially biologically controlled.
8
Al-Battashi, Huda, Sanket J. Joshi, Bernhard Pracejus y Aliya Al-Ansari. "The Geomicrobiology of Chromium (VI) Pollution: Microbial Diversity and its Bioremediation Potential". Open Biotechnology Journal 10, n.º 1 (11 de noviembre de 2016): 379–89. http://dx.doi.org/10.2174/1874070701610010379.
Texto completoResumen
The role and significance of microorganisms in environmental recycling activities marks geomicrobiology one of the essential branches within the environmental biotechnology field. Naturally occurring microbes also play geo-active roles in rocks, leading to biomineralization or biomobilization of minerals and metals. Heavy metals, such as chromium (Cr), are essential micronutrients at very low concentrations, but are very toxic at higher concentrations. Generally, heavy metals are leached to the environment through natural processes or anthropogenic activities such as industrial processes, leading to pollution with serious consequences. The presence of potentially toxic heavy metals, including Cr, in soils does not necessarily result in toxicity because not all forms of metals are toxic. Microbial interaction with Cr by different mechanisms leads to its oxidation or reduction, where its toxicity could be increased or decreased. Chromite contains both Cr(III) and Fe(II) and microbial utilization of Fe(II)- Fe(III) conversion or Cr (III) - Cr (VI) could lead to the break-down of this mineral. Therefore, the extraction of chromium from its mineral as Cr (III) form increases the possibility of its oxidation and conversion to the more toxic form (Cr (VI)), either biologically or geochemically. Cr (VI) is quite toxic to plants, animals and microbes, thus its levels in the environment need to be studied and controlled properly. Several bacterial and fungal isolates showed high tolerance and resistance to toxic Cr species and they also demonstrated transformation to less toxic form Cr (III), and precipitation. The current review highlights toxicity issues associated with Cr species and environmental friendly bioremediation mediated by microorganisms.
9
Lykoshin, D. D., V. V. Zaitsev, M. A. Kostromina y R. S. Esipov. "New-generation osteoplastic materials based on biological and synthetic matrices". Fine Chemical Technologies 16, n.º 1 (18 de marzo de 2021): 36–54. http://dx.doi.org/10.32362/2410-6593-2021-16-1-36-54.
Texto completoResumen
Objectives. The purpose of this analytical review is to evaluate the market for osteoplastic materials and surgical implants, as well as study the features of new-generation materials and the results of clinical applications.Methods. This review summarizes the volumes of research articles presented in the electronic database PubMed and eLIBRARY. A total of 129 scientific articles related to biological systems, calcium phosphate, polymer, and biocomposite matrices as carriers of pharmaceutical substances, primary recombinant protein osteoinductors, antibiotics, and biologically active chemical reagents were analyzed and summarized. The search depth was 10 years.Results. Demineralized bone matrix constitutes 26% of all types of osteoplastic matrices used globally in surgical osteology, which includes neurosurgery, traumatology and orthopedics, dentistry, and maxillofacial and pediatric surgery. Among the matrices, polymer and biocomposite matrices are outstanding. Special attention is paid to the possibility of immobilizing osteogenic factors and target pharmaceutical substances on the scaffold material to achieve controlled and prolonged release at the site of surgical implantation. Polymeric and biocomposite materials can retard the release of pharmaceutical substances at the implantation site, promoting a decrease in the toxicity and an improvement in the therapeutic effect. The use of composite scaffolds of different compositions in vivo results in high osteogenesis, promotes the initialization of biomineralization, and enables the tuning of the degradation rate of the material.Conclusions. Osteoplastic materials of various compositions in combination with drugs showed accelerated regeneration and mineralization of bone tissue in vivo, excluding systemic side reactions. Furthermore, although some materials have already been registered as commercial drugs, a plethora of unresolved problems remain. Due to the limited clinical studies of materials for use on humans, there is still an insufficient understanding of the toxicity of materials, time of their resorption, speed of drug delivery, and the possible long-term adverse effects of using implants of different compositions.
10
Bouabdellah, Mohammed, Wissale Boukirou, Adriana Potra, Erik Melchiorre, Hassan Bouzahzah, Johan Yans, Khadra Zaid et al. "Origin of the Moroccan Touissit-Bou Beker and Jbel Bou Dahar Supergene Non-Sulfide Biomineralization and Its Relevance to Microbiological Activity, Late Miocene Uplift and Climate Changes". Minerals 11, n.º 4 (11 de abril de 2021): 401. http://dx.doi.org/10.3390/min11040401.
Texto completoResumen
Through integration of Pb-Zn ± Cu non-sulfide mineralogy, texture, and stable isotope (C, O, S) geochemistry, the world-class Touissit- Bou Beker and Jbel Bou Dahar Mississippi Valley-type districts of the Moroccan Atlasic system have been investigated in order to gain insights into the origin and processes that contributed to the formation of the base metal non-sulfide mineralization. In both districts, direct replacement (“red calamine”) and wallrock replacement (“white calamine”) ores are observed. Based on the mineral assemblages, ore textures, and crosscutting relations, three distinct mineralizing stages are recognized. The earliest, pre-non-sulfide gossanous stage was a prerequisite for the following supergene stages and constituted the driving force that ultimately promoted the leaching of most base metals such as Zn and Cu and alkalis from their rock sources. The following two stages, referred to as the main supergene “red calamine” and late “white calamine” ore stages, generated the bulk of mineable “calamine” ores in the Touissit-Bou Beker and Jbel Bou Dahar districts. Stable isotope compositions (δ13CV-PDB, δ18OV-SMOW, δ34SCDT) support a three-stage model whereby metals were released by supergene acidic fluids and then precipitated by bacteria and archaea-mediated metal-rich meteoric fluids due to a decrease in temperature and/or increase of fO2. Oxygen isotope thermometry indicates decreasing precipitation temperatures with advancing paragenetic sequence from 33° to 18 °C, with wet to semi-arid to arid climatic conditions. The close spatial relationships between coexisting sulfide and non-sulfide mineralization along with stable isotope constraints suggest that the oxidation of sulfides occurred concurrently after the main stage of the Alpine orogeny between 15 Ma and the present. More importantly, the current data show for the first time the involvement of biologically controlled activity as the major driving process that triggered both oxidation and deposition of supergene mineralization at Jbel Bou Dahar and Touissit-Bou Beker districts. Conclusions drawn from this study therefore have implications for supergene Mississippi Valley-type (MVT) -derived non-sulfide deposits worldwide and account for the prominent role of biological processes in the genesis of this category of ore deposits.
Tesis sobre el tema "Biologically-Controlled biomineralization"
1
Wallace, Adam Folger. "Biologically Controlled Mineralization and Demineralization of Amorphous Silica". Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/27424.
Texto completoResumen
Living systems possess seemingly bottomless complexity. Attempts to parse the details of one cellular process from all other concurrent processes are challenging, if not daunting undertakings. The apparent depth of this problem, as it pertains to biomineralization, is related to the small number of existing studies focused on the development of a mechanism-based understanding of intracellular mineralization processes. Molecular biologists and geneticists have only begun to turn their attention towards identification and characterization of molecules involved in regulating and controlling biomineral formation. With this new knowledge, a number of new and exciting research opportunities are currently awaiting development upon a barren landscape.
Silica biomineralization is one of these emerging frontiers. As new information about the chemical and structural nature of the macromolecules involved in biosilicification is revealed, the means these species employ to control the temporal and spatial onset of silica deposition in vivo become available for exploration. The first chapter of this dissertation outlines those aspects of silicate metabolism that are directly relevant to the controlled biomineralization of silica in eukaryotic organisms and identifies pervasive and unanswered questions surrounding biosilica formation. Particular attention is paid to the diatoms, which are the most abundant, and extensively investigated silica-mineralizing organisms in modern seas. The extent, and mechanism through which specific organic moieties work individually or in concert to direct mineral formation at biological interfaces is a central concern of modern biomineralization research. Chapter two addresses this forefront issue for silica mineralizing systems, and reports the results of an experimental investigation designed to measure the effects of individual surface-bound organic functional groups on the rate of surface-directed silica nucleation. Chapter three discusses an additional aspect of this research aimed at investigating the reactivity of nanoparticulate biogenic silica produced by marine phytoplankton and terrestrial plants in natural environments. Density Functional Theory and ab initio molecular orbital calculations are employed to explore potential mechanisms underlying the catalytic activity of divalent metal cations during the hydrolysis of Si â O bonded networks.Ph. D.
2
Park, Yeseul. "Metal sulfide biomineralization by magnetotactic bacteria". Electronic Thesis or Diss., Aix-Marseille, 2022. http://www.theses.fr/2022AIXM0262.
Texto completoResumen
La biominéralisation de sulfures métalliques est observée tant dans des cultures microbiennes que dans la nature. Cependant, seulement quelques cas ont été définis comme étant des processus biologiquement contrôlés comme cela est le cas pour la greigite produite par les bactéries magnétotactiques. Pendant ma thèse, j'ai découvert un nouveau type de biominéralisation intracellulaire de sulfure métallique en étudiant l'impact du cuivre sur la biominéralisation de la greigite par la bactérie Desulfamplus magnetovallimortis BW-1.Le biominéral que j'ai identifié a une structure et une organisation cristalline originales. Les particules sont de morphologie sphérique ou ellipsoïdale et composées de sous-grains de 1 à 2 nm de sulfure de cuivre hexagonal qui reste dans un état métastable. Les particules sont situées dans le périplasme, et sont entourées d'une substance organique. Sur la base de ces observations, j'ai conclu que le biominéral est produit et conservé grâce à un contrôle biologique. En conséquence, j'ai mené des études de protéomique pour trouver des protéines associées au processus qui ont mis à jour deux protéines périplasmiques, une protéine résistante aux métaux lourds et une protéase de type DegP, qui fonctionnent probablement ensemble pour réagir au stress causé par le cuivre.Une telle biominéralisation intracellulaire est spécifique à BW-1et n'est initiée que par les ions cuivre, mais pas par d'autres ions métalliques comme le nickel, le zinc ou le cobalt. Mes recherches de doctorat révèlent donc des caractéristiques inconnues de la biominéralisation des sulfures métalliques, en particulier au sein des bactéries magnétotactiquesBiomineralization of metal sulfides has been broadly observed in microbial cultures and in nature. However, only a few cases have been reported as biologically-controlled processes, such as greigite produced by magnetotactic bacteria. I discovered a new type of intracellular metal sulfide biomineralization, while studying the impact of copper on greigite biomineralization by the magnetotactic bacterium Desulfamplus magnetovallimortis strain BW-1.The newly discovered metal sulfide biominerals are nanoscopic particles and have an interesting crystal structure and organization. These spherical or ellipsoidal particles are composed of 1-2 nm-sized sub-grains of hexagonal copper sulfide that remains in a metastable state. The particles are located in the periplasmic space, surrounded by an organic substance. Based on these observations, it was concluded that the biomineral produced and conserved is a result of biological control. Proteomics studies with cellular and particulate samples identified several proteins associated with the process. The initial result showed that two periplasmic proteins, a heavy metal resistant protein, and a DegP-like protease, are likely working together to react to the envelope stress caused by copper. Such intracellular biomineralization is organism-specific and only initiated by the increase of copper ions, but not by other metal ions like nickel, zinc, or cobalt. Overall, my work reveals unknown features of metal sulfide biomineralization, specifically within magnetotactic bacteria
Capítulos de libros sobre el tema "Biologically-Controlled biomineralization"
1
Bazylinski, Dennis A. y Richard B. Frankel. "8. Biologically Controlled Mineralization in Prokaryotes". En Biomineralization, editado por Patricia M. Dove, James J. De Yoreo y Steve Weiner, 217–48. Berlin, Boston: De Gruyter, 2003. http://dx.doi.org/10.1515/9781501509346-013.
Texto completo
2
Mann, Stephen. "Chemical control of biomineralization". En Biomineralization Principles and Concepts in Bioinorganic Materials Chemistry, 38–67. Oxford University PressOxford, 2001. http://dx.doi.org/10.1093/oso/9780198508823.003.0004.
Texto completoResumen
Abstract The high level of regulation associated with biologically controlled mineralization is fundamentally dependent on the chemical control of inorganic precipitation and crystallization. In this chapter, we review the key principles of precipitation—usually from the standpoint of ‘crystallization’ —and illustrate their relevance to biomineralization. The aim is to introduce the fundamental chemical concepts that are pivotal to the specific biological control mechanisms described in Chapters 5 to 8.
3
Lowenstam, Heinz A. y Stephen Weiner. "Protoctista". En On Biomineralization. Oxford University Press, 1989. http://dx.doi.org/10.1093/oso/9780195049770.003.0006.
Texto completoResumen
This kingdom is denned by exclusion, in that its members are neither animals, plants, fungi, nor prokaryotes. They comprise eukaryotic microorganisms and their immediate descendants (Margulis and Schwartz 1988). Of the 27 phyla that make up this kingdom, no less than 17 contain members that form mineralized hard parts. Although the vast majority of Protoctista are microorganisms, their smallness does not in any way imply an inability to control their biomineralization processes. On the contrary, many of the mineralizing Protoctista form very elaborate and complex structures. D’Arcy Thompson was one of many natural scientists who was both intrigued and fascinated by their skeletal morphologies. A perusal of his book On Growth and Form shows beautifully illustrated examples of protoctist skeletons and the text reveals a rare insight into some of the forces that govern their structure-forming processes. In the Radiolaria, for example, Thompson (1942) concludes that “the symmetry which the organism displays seems identical with that symmetry offerees which results from the play and interplay of surface- tensions in the whole system: this symmetry being displayed, in one class of cases, in a more or less spherical mass of froth, and in another class in a simpler aggregation of a few, otherwise isolated, vesicles” (p. 723). Although elegant and simple, physicochemical processes of interfacial chemistry are not sufficient to explain the complex, genetically controlled morphologies of many radiolarian species. Skeletal morphology is most likely the product of the delicate interplay between biologically controlled and physicochemically controlled processes (Anderson 1986). This is a recurring theme in biomineralization. Not all the protoctists are expert mineralizers. In fact they exhibit the whole spectrum of mineralization processes, from uncontrolled to finely tuned. Within the foraminifera and testate amoeba, among the Rhizopoda, are examples in which this wide diversity is found even within an individual phylum. They both contain species that construct their tests entirely out of organic materials or organic materials reinforced with mineral grains scavenged from the environment. They also contain species in which the test is mineralized by the organism itself, and at least in the case of the foraminifera, this can occur both intracellularly and extracellularly (Lowenstam 1986).