Les travaux réalisés ont pour but de répondre à deux questions : comment le collagène s'organise-t-il dans l'os mature ? Comment la phase minérale de l'os se forme-t-elle et quel est l'effet de son environnement sur sa formation ? Nous avons étudié d'un point de vue structural des coupes d'os en nous concentrant sur l'interface tissu ostéoïde/os mature, impliquant le front de minéralisation. Nous avons conclu qu'un domaine acide fait de collagène non fibrillaire existe à cette interface. Nous proposons ainsi un nouveau mécanisme pour la formation osseuse lors du remodelage osseux impliquant une mésophase acide de collagène au sein de laquelle l'apatite se forme. Nous avons donc étudié l'effet de cet environnement acide sur la formation d'apatite in vitro par Raman in situ et RMN du solide. Nous avons observé que la séquence de précipitation de l'apatite seule en solution passe par la formation d'une phase amorphe (ACP) qui se transforme en OCP puis en apatite. En présence de pAsp, la nucléation est ralentie et de l'OCP est stabilisé. Une grande concentration en citrate inhibe la formation de toute autre phase que l'ACP tandis qu'une plus faible concentration entraine la formation d'apatite directement depuis l'ACP. Cette séquence ACP/apatite est également observée lorsque la minéralisation est réalisée en présence de collagène quelle que soit sa concentration. Le collagène entraine la formation d'une apatite beaucoup plus désorganisée de cristallinité proche de celle de l'apatite osseuse. Enfin, une concentration en collagène supérieure à 80 mg/mL mène à la stabilisation d'une phase ionique stable à pH basique expliquant le co-alignement apatite/collagène. / This work aims to understand: How is reached the plywood architecture in bone? How is bone apatite formed and what is the effect of the environment on apatite formation? Thus, histological bone thin sections were investigated focusing on the interface between the osteoid and mature bone tissues. Our results show that this interface is acidic and collagenic but not in the form of fibrils. Thus, we propose a new mechanism for bone formation in bone remodelling where osteoclasts dissolution and new fibrils formation from osteoblasts lead to the formation of an acidic collagen mesophase in which apatite is then formed. In such mechanism, apatite forms from an acidic solution in interaction with an organic matrix (collagen molecules, citrate and non-collagenous proteins). Acidic biomimetic models have been set and the apatite formation has been followed in vitro using in situ Raman and ssNMR spectroscopies. Without organic molecules, biomimetic apatite is formed through the precipitation of an amorphous phase (ACP) that transforms into OCP which then turns into apatite. With pAsp, the same scenario is observed but the nucleation is delayed and residual OCP is stabilized. With a high concentration of citrate, only ACP is observed whereas with a lower concentration formation of OCP is inhibited. The same sequence is also observed with collagen but the final product is a more disorganized apatite. Apatite formation in dense and organized collagen solutions leads to the formation of a liquid ionic solution stable at basic pH during the first 72 hours explaining the resulting apatite/collagen co-alignement.

Viruses are ubiquitous biological entities whose importance and role in aquatic habits is beginning to take form. However, several habitats have undergone limited to no examination with viral-geochemical parameters minimally examined and viral-mineral relationships in the natural environment and the role of mineralization on viral-host dynamic completely lacking. To further develop knowledge on the presence and abundances of viruses, how viruses impact aquatic systems, and how viral-host interactions can be impacted under mineralizing conditions, viruses were examined under a variety of habitats and experimental conditions. Water samples were collected from the deep subsurface (up to 450 m underground) and acid mine drainage (AMD) systems in order to determine the presence, abundance, and viral-geochemical relationships within the systems. Samples were also collected from a variety of freshwater habitats, which have undergone limited examination, to determine viral-geochemical and viral-mineral relationships. Lastly, bacteriophage-host dynamics were examined under authigenic mineral precipitation to determine how mineralization impacts this relationship. Results reveal that not only are viruses present in the deep subsurface and AMD systems, but they are abundant (up to 107 virus-like particles/mL) and morphogically diverse. Viruses are also the strongest predictor of prokaryotic abundance in southern Ontario freshwater systems where potential nutrients are rich. Geochemical variables, such as pH and Eh, were shown to have negative impacts of viral abundance indicting that AMD environments are detrimental for free viruses (i.e. not particle associated). Direct evidence of viral-mineral interactions was found using transmission electron microscopy as viral particles were shown attached to iron-bearing mineral phases (determined through elemental analysis). In addition, evidence of viral participation in mineralization events was found in both AMD and freshwater environments where inverse correlations were noted between viral abundance and jarosite saturation indices (r = -0.71 and r = -0.33, respectively), and goethite saturation indices were also noted to be the strongest predictor of VLP abundance in freshwater habitats explaining 78% of the variability in the data. Lastly, iron precipitation and/or metal ion binding to bacterial surfaces greatly reduced phage replication (~98%) revealing bacterial mineralization has a protective benefit strongly hindering viral replication.

Viruses are ubiquitous biological entities whose importance and role in aquatic habits is beginning to take form. However, several habitats have undergone limited to no examination with viral-geochemical parameters minimally examined and viral-mineral relationships in the natural environment and the role of mineralization on viral-host dynamic completely lacking. To further develop knowledge on the presence and abundances of viruses, how viruses impact aquatic systems, and how viral-host interactions can be impacted under mineralizing conditions, viruses were examined under a variety of habitats and experimental conditions. Water samples were collected from the deep subsurface (up to 450 m underground) and acid mine drainage (AMD) systems in order to determine the presence, abundance, and viral-geochemical relationships within the systems. Samples were also collected from a variety of freshwater habitats, which have undergone limited examination, to determine viral-geochemical and viral-mineral relationships. Lastly, bacteriophage-host dynamics were examined under authigenic mineral precipitation to determine how mineralization impacts this relationship. Results reveal that not only are viruses present in the deep subsurface and AMD systems, but they are abundant (up to 107 virus-like particles/mL) and morphogically diverse. Viruses are also the strongest predictor of prokaryotic abundance in southern Ontario freshwater systems where potential nutrients are rich. Geochemical variables, such as pH and Eh, were shown to have negative impacts of viral abundance indicting that AMD environments are detrimental for free viruses (i.e. not particle associated). Direct evidence of viral-mineral interactions was found using transmission electron microscopy as viral particles were shown attached to iron-bearing mineral phases (determined through elemental analysis). In addition, evidence of viral participation in mineralization events was found in both AMD and freshwater environments where inverse correlations were noted between viral abundance and jarosite saturation indices (r = -0.71 and r = -0.33, respectively), and goethite saturation indices were also noted to be the strongest predictor of VLP abundance in freshwater habitats explaining 78% of the variability in the data. Lastly, iron precipitation and/or metal ion binding to bacterial surfaces greatly reduced phage replication (~98%) revealing bacterial mineralization has a protective benefit strongly hindering viral replication.

Uranium contaminations of the subsurface in the vicinity of nuclear materials processing sites pose a health risk as the uranyl ion in its oxidized state, U(VI), is highly mobile in aquifers. Current remediation strategies such as pump and treat or excavation are invasive and expensive to implement on a large scale. In situ bioremediation represents an alternative strategy that uses the ability of local microbial communities to immobilize contaminants and is actively studied for uranium remediation. The immobilization of U(VI) in groundwater is achieved either by bioreduction to solid uraninite (U(IV)), adsorption to the soil matrix, or non-reductive precipitation of uranium phosphate minerals through the activity of bacterial phosphatases. Bioreduction has been widely studied for remediation of the saturated zone, as anaerobic conditions typically prevail in these environments. This process is only efficient at circumneutral pH, however, and the end product uraninite is unstable under aerobic conditions or in the presence of manganese oxides, nitrite, or even freshly formed iron oxides. Although non-reductive biomineralization of uranium catalyzed by bacterial phosphatase activity successfully removes uranium from the vadose zone, further studies are needed to assess the ability of microbial communities to hydrolyze organophosphate compounds in the saturated zone where oxygen is often depleted and uranium bioreduction may be significant. To investigate this process under anaerobic conditions, low pH soil samples from a uranium contaminated site at the Oak Ridge Field Research Center were incubated anaerobically in flow through reactors in the presence of exogenic organophosphate compounds to stimulate the natural microbial communities in the original soil matrix. Aqueous uranium was injected continuously in the reactors to determine the fraction of uranium removed during these incubations. The reactors amended with organophosphate produced inorganic phosphate in the effluent, suggesting that bacterial phosphatase activity can be stimulated even in anaerobic environments at low pH. Removal of U(VI) in a control amended with organophosphate over a short time period was similar compared to reactors amended with organophosphate for long times suggesting that adsorption may also play a role in U(VI) immobilization. A sequential extraction technique was optimized to differentiate the fraction of uranium loosely adsorbed and the fraction of uranium precipitated as phosphate minerals and batch adsorption experiments were performed to obtain thermodynamic parameters that could be used to predict the fraction of U(VI) adsorbed onto the soil matrix. Results indicated that 100% uranium adsorption was favorable from pH 5 to 10 (without the presence of phosphate), and that most of the solid phase uranium was extracted in the step defined for the strongly adsorbed/uranium phosphate mineral in both long and short-term amended reactors. Overall, these results demonstrate that the biomineralization of uranium phosphate minerals is a viable bioremediation strategy in both the vadose and saturated zones of aquifers at both low and high pH, provided an organophosphate source is available.

With respect to the principles of biomineralization, it is of interest to study the crystallization of calcium oxalates under various experimental conditions. Calcium oxalates play decisive roles as biominerals in plants and as pathological “urinary/kidney stones” in vertebrates. Calcium oxalate exists in three different hydration states; calcium oxalate monohydrate (COM, monoclinic, a = 6.290(1)Å, b = 14.583(1)Å, c = 10.116(1)Å, β = 109.46°, P21/c), calcium oxalate dihydrate (COD, tetragonal, a = b = 12.371(3)Å, c = 7.357(2)Å, α = β = γ = 90°, I4/m) and calcium oxalate trihydrate (COT, triclinic, a = 6.11(1)Å, b = 7.167(2)Å, c = 8.457(2)Å, α = 76.5(2)°, β = 70.35(2)°, γ = 70.62(2)°, P ). Monoclinic COM and tetragonal COD are the most common phyto-crystals and the main constituents of kidney and urinary stones. The occurrence of calcium oxalates in plants represents a useful biogenesis (protection against herbivores) unlike the devastating occurrence in renal tubules. Therefore, biomineralization can be physiological or pathological. A systematic investigation of the morphological evolution of calcium oxalates in the presence of organic components is essential for understanding the mechanism of “pathological biomineralization”. In order to understand the pathological biomineralization of uroliths, it is necessary grow calcium oxalates comparable in morphology under similar growth conditions. The formation of calcium oxalate stones within a gelatinous state of proteins, polysaccharides, lipids and other biomacromolecules under a flow of supersaturated urine supports the fact that an “organic” gel model can simulate the process of urinary stone formation under in vitro conditions. Furthermore, synthetic polymers with precisely known functions and solution behaviours are better choices to understand the interaction of acidic proteins with calcium oxalates. Therefore, as a first step to unravel the complex pathology of uro/nephro lithiasis, we started to examine the structure and morphology of calcium oxalates crystallized in the presence of organic additives such as the sodium salt of polyacrylic acid (PAA) as well as agar gel. The influence of initial calcium oxalate concentration, pH and concentration of the additives on the formation of hydration states of calcium oxalates have been investigated along with the stated general methods. Apart from the three hydrated forms, calcium oxalate exists also in the anhydrous form (COA). Although three modifications of COA (α, β and γ) are reported in the literatures, the crystal structures and phase transformations were controversially discussed. We have been able to reveal the crystal structure of the β-modification of the anhydrous calcium oxalate by a combination of atomistic simulations and Rietveld refinements on the basis of powder X-ray diffraction pattern. β-COA belongs to the monoclinic system with unit cell parameters, a = 6.1644(3)Å, b = 7.3623(2)Å, c = 9.5371(5)Å, β = 90.24(2)°, P2/m (No. 10). The dehydration of COM was mimicked in silico to receive an initial model of the crystal structure of anhydrous calcium oxalate. This general approach may also be accessible for other decomposition processes ending up with crystalline powders of unknown crystal structure. No evidence for transformations from or to the α- or γ- modifications was found during our investigations. The growth pattern of COD crystals precipitated from aqueous solutions in the presence of PAA is clearly dependent on the concentration of PAA. By increasing the concentration of PAA, the shape of COD has been found to change from tetragonal bi-pyramids with dominant (101) pyramidal faces to tetragonal prisms with dominant (100) prism faces and finally to dumbbells. At still higher PAA concentrations, the morphology is reverted back to rod-like tetragonal prisms. Apart from these experiments, the interaction of PAA with (100) and (101) crystal faces of COD was explored with the aid of atomistic simulations. The simulation confirmed that during the development of the aggregates, strong interactions of PAA with the (100) faces take over control of morphologies. Our investigations show that the inner architecture of all the morphological varieties of COD was found to be dominated by an inner “core” consisting of thin elongated crystallites together with incorporated PAA and an outer “shell” formed as a consequence of secondary nucleation processes. We propose that for all types of COD aggregates, relative proportion of calcium oxalate and PAA dictates the shape and formation of nanometer sized crystallites which then aggregate and align to form the core. Such cores enriched with PAA may act as the sites for secondary nucleation events of calcium oxalate crystallites which then cover the core like a shell. In vitro experimental models for the growth of calcium oxalates can give valuable information on the growth and aggregation of urinary stones. Therefore, the “double diffusion technique” in agar gel matrix has been used for the biomimetic growth of calcium oxalate (COM) stones. A great variety of morphological forms of COM are produced in agar gel matrices (2 wt.-% agar gel of pH 8.5) ranging from platy crystallites to dumbbells and spherulites. The COM dumbbells and spherulites are assumed to be formed by the aggregation of smaller crystallites as a consequence of increased supersaturation inside the gel. Moreover, an increase of the pH value of the agar gel has been found to suppress the growth of COM and favours the growth of COD. The morphology of COD crystals grown in 2 wt.-% agar gel of pH 11.5 includes tetragonal prisms and dumbbells. The system calcium oxalate/ PAA/ H2O is a suitable model system for the investigation of principles of biomineral growth (shape development) in general. Our results demonstrate that the double diffusion technique in agar gel is a convenient route to grow calcium oxalate aggregates showing close resemblance to biogenic calculi and to study their ontogeny.

Lowering the Maximum Contaminant Level (MCL) for arsenic in drinking water in the U.S., has caused a significant increase in the volume of Arsenic Bearing Solid Residuals (ABSRs) generated by drinking water utilities. Most of the affected utilities are smaller water treatment facilities, especially in the arid Southwest, and are expected to use adsorption onto solid sorbents for arsenic removal. Because of their high adsorption capacity and low cost, iron sorbents are used treatment technology and, when the sorbent's capacity is spent, these ABSRs are disposed in municipal solid waste (MSW) landfills and as a consequence arsenic is likely being released into leachate. However, a mature landfill is a biotic, reducing environment, which causes arsenic reduction and mobilization from the ABSRs. It is well documented that iron and sulfur redox cycles largely control arsenic cycling and, because iron and sulfur are ubiquitous in MSW, it is suspected that they play key roles in arsenic disposition in the landfill microcosm. The purpose of this study is to investigate the degree to which sulfate can prevent arsenic from leaching into landfill through biomineralization and to study ABSRs biogeochemical weathering effect on arsenic sequestration. The primary routes of iron and sulfate reduction in landfills are microbially mediated and biomineralization is a common by-product. In this case, biomineralization is the transformation of ferric (hydr) oxides into ferrous iron phase and sulfate into sulfide minerals such as: siderite (FeCO₃), vivianite (Fe₃(PO₄)₂), iron sulfide (FeS), goethite (α-FeOOH), and realgar (AsS). In this work, long-term microbial reduction and biomineralization of iron, sulfur, and arsenic species are evaluated as processes that both cause arsenic release from landfilled ABSRs and may possibly provide a means to re-sequester As in a recalcitrant solid state. The work uses long-term, continuous flow-through laboratory-scale columns in which controlled conditions similar to those found in a mature landfill prevail. In these simulated landfill column experiments, formation of biominerals, same as those that would naturally occur in typical non-hazardous MSW landfills, will be investigated. The feed contains lactate as the carbon source and primary electron donor, and ferric iron, arsenate, and a range of sulfate concentrations as primary electron acceptors. Our results suggest that biomineralization changes the stability of arsenic through a number of different processes including (i) release of arsenic through reductive dissolution of iron-based ABSRs; and (ii) readsorption/incorporation of released arsenic to secondary biominerals. The influence of biominerals, which have less surface area and adsorption capacity than original AFH, on the retention of arsenic is also investigated in this study. Our results show that the concentration of sulfate fed to the system affects the biomineral formation, and that the relative amounts and sequence of precipitation of biominerals affect the free arsenic concentration that can seemingly be engineered by the concentration of sulfate fed to the system. Comparison between the columns with different sulfate concentrations indicate that inflow sulfate concentration higher than 2.08 mM decreases As mobilization to <50%.

No description available.

Biological materials have ever been used by humans because of their remarkable properties. This is surprising since the materials are formed under physiological conditions and with commonplace constituents. Nature thus not only provides us with inspiration for designing new materials but also teaches us how to use soft molecules to tune interparticle and external forces to structure and assemble simple building blocks into functional entities. Magnetotactic bacteria and their chain of magnetosomes represent a striking example of such an accomplishment where a very simple living organism controls the properties of inorganics via organics at the nanometer-scale to form a single magnetic dipole that orients the cell in the Earth magnetic field lines. My group has developed a biological and a bio-inspired research based on these bacteria. My research, at the interface between chemistry, materials science, physics, and biology focuses on how biological systems synthesize, organize and use minerals. We apply the design principles to sustainably form hierarchical materials with controlled properties that can be used e.g. as magnetically directed nanodevices towards applications in sensing, actuating, and transport. In this thesis, I thus first present how magnetotactic bacteria intracellularly form magnetosomes and assemble them in chains. I developed an assay, where cells can be switched from magnetic to non-magnetic states. This enabled to study the dynamics of magnetosome and magnetosome chain formation. We found that the magnetosomes nucleate within minutes whereas chains assembles within hours. Magnetosome formation necessitates iron uptake as ferrous or ferric ions. The transport of the ions within the cell leads to the formation of a ferritin-like intermediate, which subsequently is transported and transformed within the magnetosome organelle in a ferrihydrite-like precursor. Finally, magnetite crystals nucleate and grow toward their mature dimension. In addition, I show that the magnetosome assembly displays hierarchically ordered nano- and microstructures over several levels, enabling the coordinated alignment and motility of entire populations of cells. The magnetosomes are indeed composed of structurally pure magnetite. The organelles are partly composed of proteins, which role is crucial for the properties of the magnetosomes. As an example, we showed how the protein MmsF is involved in the control of magnetosome size and morphology. We have further shown by 2D X-ray diffraction that the magnetosome particles are aligned along the same direction in the magnetosome chain. We then show how magnetic properties of the nascent magnetosome influence the alignment of the particles, and how the proteins MamJ and MamK coordinate this assembly. We propose a theoretical approach, which suggests that biological forces are more important than physical ones for the chain formation. All these studies thus show how magnetosome formation and organization are under strict biological control, which is associated with unprecedented material properties. Finally, we show that the magnetosome chain enables the cells to find their preferred oxygen conditions if the magnetic field is present. The synthetic part of this work shows how the understanding of the design principles of magnetosome formation enabled me to perform biomimetic synthesis of magnetite particles within the highly desired size range of 25 to 100 nm. Nucleation and growth of such particles are based on aggregation of iron colloids termed primary particles as imaged by cryo-high resolution TEM. I show how additives influence magnetite formation and properties. In particular, MamP, a so-called magnetochrome proteins involved in the magnetosome formation in vivo, enables the in vitro formation of magnetite nanoparticles exclusively from ferrous iron by controlling the redox state of the process. Negatively charged additives, such as MamJ, retard magnetite nucleation in vitro, probably by interacting with the iron ions. Other additives such as e.g. polyarginine can be used to control the colloidal stability of stable-single domain sized nanoparticles. Finally, I show how we can “glue” magnetic nanoparticles to form propellers that can be actuated and swim with the help of external magnetic fields. We propose a simple theory to explain the observed movement. We can use the theoretical framework to design experimental conditions to sort out the propellers depending on their size and effectively confirm this prediction experimentally. Thereby, we could image propellers with size down to 290 nm in their longer dimension, much smaller than what perform so far. / Biologische Materialien wie Knochen, Muscheln und Holz wurden von den Menschen seit den ältesten Zeiten verwendet. Diese biologisch gebildeten Materialien haben bemerkenswerte Eigenschaften. Dies ist besonders überraschend, da sie unter physiologischen Bedingungen und mit alltäglichen Bestandteilen gebildet sind. Die Natur liefert uns also nicht nur mit Inspiration für die Entwicklung neuer Materialien, sondern lehrt uns auch, wie biologische Additiven benutzen werden können, um einfache synthetische Bausteine in funktionale Einheiten zu strukturieren. Magnetotaktischen Bakterien und ihre Kette von Magnetosomen sind ein Beispiel, wo einfache Lebewesen die Eigenschaften von anorganischen Materialien steuern, um sich entlang den magnetischen Feldlinien der Erde zu orientieren. Die von den Bakterien gebildeten Magnetosomen sind von besonderem Interesse, da mit magnetischen Eisenoxid-Nanopartikeln in den letzten zehn Jahren einer Vielzahl von Bio-und nanotechnologischen Anwendungen entwickelt worden sind. In dieser Arbeit stelle ich eine biologische und eine bio-inspirierte Forschung auf der Grundlage der magnetotaktischen Bakterien vor. Diese Forschung verbindet die neuesten Entwicklungen von Nanotechnik in der chemischen Wissenschaft, die neuesten Fortschritte der Molekularbiologie zusammen mit modernen Messverfahren. Mein Forschungsschwerpunkt liegt somit an der Schnittstelle zwischen Chemie, Materialwissenschaften, Physik und Biologie. Ich will verstehen, wie biologische Systeme Materialien synthetisieren und organisieren, um Design-Prinzipien zu extrahieren, damit hierarchischen Materialien mit kontrollierten Eigenschaften nachhaltig gebildet werden.

Biomineralization is a process encompassing all mineral containing tissues produced within an organism. The most dynamic example of this process is the formation of the mollusk shell, comprising a variety of crystal phases and microstructures. The organic component incorporated within the shell is said to dictate this remarkable architecture. Subsequently, for the past decade considerable research have been undertaken to identify and characterize the protein components involved in biomineralization. Despite these efforts the general understanding of the process remains ambiguous. This study employs a novel molecular approach to further the elucidation of the shell biomineralization. A microarray platform has been custom generated (PmaxArray 1.0) from the pearl oyster Pinctada maxima. PmaxArray 1.0 consists of 4992 expressed sequence tags (ESTs) originating from the mantle, an organ involved in shell formation. This microarray has been used as the primary tool for three separate investigations in an effort to associate transcriptional gene expression from P. maxima to the process of shell biomineralization. The first investigation analyzes the spatial expression of ESTs throughout the mantle organ. The mantle was dissected into five discrete regions and each analyzed for gene expression with PmaxArray 1.0. Over 2000 ESTs were differentially expressed among the tissue sections, identifying five major expression regions. Three of these regions have been proposed to have shell formation functions belonging to nacre, prismatic calcite and periostracum. The spatial gene expression map was confirmed by in situ hybridization, localizing a subset of ESTs from each expression region to the same mantle area. Comparative sequence analysis of ESTs expressed in the proposed shell formation regions with the BLAST tool, revealed a number of the transcripts were novel while others showed significant sequence similarities to previously characterized shell formation genes. The second investigation correlates temporal EST expression during P. maxima larval ontogeny with transitions in shell mineralization during the same period. A timeline documenting the morphologicat microstructural and mineralogical shell characteristics of P. maxima throughout larval ontogeny has been established. Three different shell types were noted based on the physical characters and termed, prodissoconch I, prodissoconch 11 and dissoconch. PmaxArray 1.0 analyzed ESTs expression of animals throughout the larval development of P. maxima, noting up-regulation of 359 ESTs in association with the shell transitions from prodissoconch 1 to prodissoconch 11 to dissoconch. Comparative sequence analysis of these ESTs indicates a number of the transcripts are novel as well as showing significant sequence similarities between ESTs and known shell matrix associated genes and proteins. These ESTs are discussed in relation to the shell characters associated with their temporal expression. The third investigation uses PmaxArray 1.0 to analyze gene expression in the mantle tissue of P. maxima specimens exposed to sub-lethal concentrations of a shell-deforming toxin, tributyltin (TBT). The shell specific effects of TBT are used in this investigation to interpret differential expression of ESTs with respect to shell formation functions. A lethal and sublethal TBT concentration range was established for P. maxima, noting a concentration of 50 ng L- 1 TBT as sub-lethal over a 21 day period. Mantle tissue from P. maxima animals treated with 50 ng L- 1 TBT was assessed for differential EST expression with untreated control animals. A total of 102 ESTs were identified as differentially expressed in association with TBT exposure, comparative sequence identities included an up-regulation of immunity and detoxification related genes and down-regulation of several shell matrix genes. A number of transcripts encoding novel peptides were additionally identified. The potential actions of these genes are discussed with reference to TBT toxicity and shell biomineralization. This thesis has used a microarray platform to analyze gene expression in spatial, temporal and toxicity investigations, revealing the involvement of numerous gene transcripts in specific shell formation functions. Investigation of thousands of transcripts simultaneously has provided a holistic interpretation of the organic components regulating shell biomineralization.

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Dr. Joel Kostka, Florida State University, College of Arts and Sciences, Dept. of Oceanography. Title and description from dissertation home page (viewed June 22, 2005). Document formatted into pages; contains xi, 108 pages. Includes bibliographical references.