The research detailed in this dissertation is focused on the use of biomolecules (i.e., peptides and proteins) to form non-biologically produced materials under mild reaction conditions (i.e, neutral pH, aqueous solutions, and room temperature). The peptides utilized in the studies detailed in this dissertation were identified through the screening of single crystal rutile TiO2 substrates or Ge powder with a phage-displayed peptide library. Twenty-one peptides were identified which possessed an affinity for Ge. Those peptides possessing a basic isoelectric point as well as hydroxyl- and imidazole-containing amino acid residues were found to be the most effective in precipitating amorphous germania from an alkoxide precursor. The phage-displayed peptide library screening of TiO2 substrates yielded twenty peptides. The titania formation activity of these peptides was found to correlate with the number of positive charges they carried. The titania materials generated by the library-identified and designed peptides were found to be composed of amorphous titania as well as <10 nm anatase and/or monoclinic TiO2 crystallites. Four recombinant proteins, derived from the amino acid sequences of proteins (silaffins) associated with biosilicification in diatoms, were also investigated for titania precipitation activity. The two most basic of these recombinant silaffins, rSil1L and rSilC, were able to induce the formation of titania. The titania precipitates generated by rSil1L were found to be similar to those produced by the phage-displayed library identified peptides. The second recombinant silaffin, rSilC, was found to produce hollow spheres of titania, which, following dehydration, were observed to transform into larger, solid spheres composed of radially aligned columns of rutile TiO2. The highly repetitive nature of the rSilC s amino acid sequence is believed to be responsible for the differences in TiO2 polymorph generated by the different recombinant silaffins and peptides. This dissertation also details research conducted on the formation of titania utilizing rSilC conjugated to synthetic and biogenic silica surfaces. These silica surfaces were functionalized with a newly developed drendritic growth technique. The dendritic functional-group amplification process was demonstrated to increase the loading of hexahisitidine tagged proteins on silica surfaces by more than 40%, as compared to traditional immobilization procedures.

Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Sandhage, Kenneth; Committee Co-Chair: Kröger, Nils; Committee Co-Chair: Naik, Rajesh; Committee Member: Hud, Nicholas; Committee Member: Marder, Seth.

This report on the diatoms (Bacillariophyta) of the Sundays and Great Fish rivers is divided into two sections. In Volume 1 the taxonomy of the diatoms from these two river systems is examined. A total of 331 taxa were studied, of which 5 are described as new species. Two taxa are given new names, since they were previously known under later homonyms. Twenty seven taxa were recorded for the first time from South Africa, while a number of species are given amended descriptions in the light of fresh information obtained concerning them. A few taxa (chiefly South African forms) have been united with previously described taxa. For the remainder of the taxa mentioned in the text, comments are passed with regard to their taxonomy and dimensions, based on facts gained through literature surveys and personal observations of the relevant taxa. As far as possible all taxa examined in Volume 1 are illustrated, and these illustrations are presented in Volume 3 of this study. Volume 2 deals with the ecology of the diatoms in the Sundays River. Special emphasis is laid on relating the composition of the diatom associations at the selected stations to the ambient salinity and ionic composition of the water. A new index, the Salinity Tolerance Index (STI), is proposed to summarize by means of a numerical value the information obtained from the analysis of a diatom association with respect to the character of the component taxa, and to indicate whether the association is derived from a freshwater, brackish water or marine source. The efficacy of the STI is evaluated in the text. The effect of the geological formations of the Sundays River valley and the underground waters emanating from them is discussed in the text. The consequences of a severe drought in the lower Sundays River, including hypersaline water in the upper estuary, on the diatom flora are also investigated.

The purpose of this research was to examine the colonization process and relationship of physico-chemical parameters to diatom and protozoan communities colonizing polyurethane foam (PF) artificial substrates in lentic habitats. This was the first study to utilize multivariate techniques for comparison of protozoan and diatom communities The following hypotheses were examined in this study: 1. diatom and protozoan species accrual is similar because the organisms are approximately the same size and share similar ecological conditions, 2. protozoan assemblages are influenced by the physicochemical parameters of their environment, and 3. diatoms and photosynthetic protozoans are more closely related to the physico-chemical parameters of their environment than are the protozoans of all trophic groups. PF substrates were placed in the littoral zone of lentic habitats. Substrates were sampled through a time series and examined for their diatom and protozoan species' presence-absences. The first hypothesis was tested by using the MacArthur-Wilson equilibrium model and by fitting the data to the model by non·linear least squares regression. Protozoan species accrual fit the model in most cases, while diatom species accrual did not. The second part of the research dealt with five lentic habitats in northern lower Michigan which were sampled as described above and concurrent with organismal sampling several physico-chemical parameters were sampled. These environmental parameters included pH, alkalinity, conductivity, temperature, and concentrations of dissolved oxygen, chloride, silica, ammonia, and total and ortho-phosphate. Protozoan communities were examined using reciprocal averaging ordination. It was found that the bog and marsh had distinct communities, while the three lakes did not. Several physicochemical parameters and factors correlated significantly with axes generated by samples in species space. The final section tested the degree of relationship among diatoms, autotrophic protozoans, and protozoans to the physicochemical parameters and factors. pH had the highest correlations with the first axes for each group. Diatom communities had the greatest degree of relationship to the physico-chemical parameters, evidence for this is provided by the greatest number of correlations between ordination axes and the physico-chemical parameters and factors. / Ph. D. / incomplete_metadata

Presently within the scientific literature no terrestrial biogenic silica models exist that compare by magnitude, processes transporting silica. Change in vegetation type has the potential to alter dissolved concentrations of Si in rivers and ultimately the oceans. Diatoms greatly depend on Si concentrations for growth, and as a result land cover change may have influenced onset diatom radiation during the Cenozoic. To expand our understanding of this cycle, a terrestrial biogenic silica model is proposed. This model accounts for biogenic silica production, dissolution and leaching through soils, as well as providing estimates for annual silica soil storage. A case study performed using the constructed biogenic silica model, showed an increase in oceanic DSi concentration during the Miocene (period of diatom diversification). However, this increase does not appear to have been sufficient to trigger global diatom radiation, suggesting multiple geographically isolated locations for this diversification.

In this study diatom distribution within the lower Save River, Mozambique, has been identified from surface sediments, surface water, mangrove cortex and buried sediments. Sandy units, bracketing a geographically extensive clay layer, have been dated with optical stimulated luminescence (OSL). Diatom analysis has been used to interpret the spatial salinity gradient and to discuss taphonomic processes within the delta. Previously, one study has been performed in the investigated area and it is of great importance to continue to identify diatom distributions since siliceous microfossils are widely used for paleoenvironmental research. Two diatom taxa, which were not possible to classify to species level have been identified; Cyclotella sp. and Diploneis sp. It is suggested that these represent species not earlier described; however they are assigned a brackish water affinity. Diatom analysis from surface water, surface sediments and mangrove cortex indicate a transition from ocean water to a dominance of freshwater taxa c. 10 km upstream the delta front. Further, ratios between marine/brackish taxa for samples from surface water and surface sediments do not correspond. It is therefore suggested that diatoms in surface sediments underestimate prevailing salinity conditions in water. In the investigated area extensive taphonomic processes seem to have large impact on diatom frustules in sediments and may bias interpretations. Therefore it is recommended to carefully investigate geology, geomorphology and vegetation before diatom analysis is applied in studies of delta paleoenvironments.

Orientador: Carlos Eduardo de Mattos Bicudo / Resumo: O estudo objetivou o inventário taxonômico dos gêneros, espécies e variedades taxonômicas da família Bacillariaceae presentes no Estado de São Paulo. A família Bacillariaceae compreende as diatomáceas com fíbulas na região interna da valva e frústula longilínea dos tipos fusiforme ou mais ou menos alongado, linear, lanceolado assimétrico, sigmoide, panduriforme ou elíptico. As estrias são lineares, uni ou bisseriadas e paralelas entre si na maioria das espécies. Os polos podem ser rostrados, capitados, obtusos, apiculados ou arredondados. A família é constituída por 18 gêneros que podem ocorrer em ambientes marinhos, estuarinos ou de água doce, sendo Nitzschia Hassal o mais especioso de todos. No Estado de São Paulo foram realizados estudos de cunho ecológico para os quais foram identificados 17 táxons em nível infragenérico e outros 13 em nível gênero. Entretanto, nenhum estudo sobre a taxonomia das Bacillariaceae foi realizado no Estado. O presente estudo contribui para o levantamento florístico das diatomáceas do Estado de São Paulo e serve de molde para realização de estudos congêneres em outros estados brasileiros. As análises foram realizadas utilizando amostras depositadas no Herbário Científico do Estado “Maria Eneyda P. Kauffmann Fidalgo” (SP) do Instituto de Botânica. Estas amostras vêm sendo coletadas desde 1960 e representam a essência da pesquisa. O plâncton foi coletado pelo arrasto subsuperficial de rede cônica confeccionada com tecido de náilon com malha de ab... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Study aimed at surveying the Bacillariaceae, including genera, species and varieties, occurring in the state São Paulo. The Bacillariaceae family comprises diatoms with fibulae in the internal region of the valve. The frustule may show various shapes as follows: short or long, straight, asymmetric lanceolate, panduriform and elliptic. Striae are uni or biseriate and parallel in most species. Valve ends may be rostrate, capitate, cuneate, obtuse, apiculate, and rounded. The family comprises 18 genera that may occur in marine, estuarine and freshwater environments. Nitzschia Hassal is the most specious genus. São Paulo state Bacillariaceae studies were mostly conducted with an ecological approach, identifying 17 taxa at infrageneric and 13 at generic level. Regrettably, no surveys were carried out aiming at the Bacillariceae floristics for that territory. Present study will improve the diatoms survey for the state São Paulo, and will provide a template for other Brazilian states. Analyses were made using samples deposited at the “Maria Eneida P. Kauffmann Fidalgo” Herbarium that belongs to the Botanical Institute of São Paulo. These samples have been collected since 1960 and represent the core of this research. Plankton samples were collected using subsurface towings with a conic 20 μm mesh nylon net. Periphyton was sampled by squeezing submerged plants and/or collecting whole submerged plants for later scraping at the laboratory. Rocks were also scraped using knives or razor b... (Complete abstract click electronic access below) / Doutor

Dust-borne iron plays an important role in modulating climate. Iron is a necessary micronutrient, crucial to growth of phytoplankton that fix atmospheric carbon dioxide into organic carbon. Bioavailable iron is relatively scarce in the oxygenated ocean due to the low solubility of oxidized iron, and it limits primary production in many ocean regions. Increased dust-borne iron reaching iron-limited regions is associated with lower atmospheric carbon dioxide, due to more complete utilization of new nitrogen (the biological pump). Since iron solubility in the ocean is low, most iron is in the solid phase, including particles and colloids from dust and insoluble iron oxyhydroxide minerals that precipitate when there is high dissolved iron not chelated by organic ligands. The chemical form (speciation) of iron greatly impacts its solubility, yet the mechanisms of solid-phase iron utilization by diatoms and the impact of solid-phase iron speciation on dust-borne iron bioavailability are not well known. Glacial activity has been associated with highly soluble minerals, but the impact of glacial activity on bioavailable iron supply has not previously been quantified. In this dissertation, I investigate the role of solid-phase dust-borne iron speciation on its bioavailability to iron-efficient diatoms, and its possible role in modulating climate through the efficiency of the biological pump in the Southern Ocean. In Chapter 1, I show that primary iron(II) silicates mobilized from bedrock through glacial physical weathering are more bioavailable than chemical weathering products such as iron(III)-rich iron oxyhydroxides and secondary clay minerals. In Chapter 2, I show that diatoms use solid-phase iron more efficiently when surface contact between the cell and particle is allowed, suggesting a mechanism of solid-phase iron utilization in addition to bulk solubility. In Chapter 3, I show that glacial activity increases the relative bioavailability of dust-borne iron reaching the Southern Ocean, by increasing the iron(II) silicate content. Finally, in Chapter 4, I present evidence that suggests physical weathering of iron(II)-rich bedrock controls the speciation and bioavailability of particulate iron across the globe. Thus, it is important to consider global and temporal changes in dust-borne iron speciation and the proximity of dust and phytoplankton cells when modeling carbon dioxide drawdown by iron fertilization of phytoplankton. It is also important to consider the relative importance of physical versus chemical weathering to understand iron fertilization on all timescales, and the relative importance of biotic and abiotic carbon dioxide drawdown.

Sediments from 21 Oregon lakes were analyzed for seven metals (Fe, Mn, Zn, Cu, Co, Ni, V) in three forms (exchangeable, organic+sulfides, and oxyhydroxides+ oxides+ carbonates) using a sequential fractionation procedure. The summer epilimnetic filterable concentration of an eighth (Mo) was also determined. Sedimentary diatom remains and summer phytoplankton populations of the lakes were correlated with the 22 metal parameters and with conservative water chemistry parameters, estimators of lake productivity, and watershed geology. Both the sedimentary metals and the two populations of primary producers correlated best with the ecoregions of Omernik and Gallant (1986). A number of species possessed correlations with specific trace metal extractions or ratios of those extractions. Bloom-forming Anabaenas strongly correlated with sedimentary organic and filterable epilimnetic nickel. Possible Ni limitation of this group was observed in one Cascade lake (Lava). The ratio of organic nickel to cobalt appeared to control the abundance of several sedimentary diatoms. Organic vanadium strongly correlated with a number of diatoms, particularly in the genera, Cyclotella and Fragilaria. Possible V pollution was observed in one lake (Woahink), and frustule remains of C. stelligera significantly increased with increasing total sedimentary V concentrations there. Zinc was the trace metal most frequently found to apparently limit diatom growth. Diatoms may have developed three different responses to Zn limitation; the three groups have been labelled affinity-, velocity-, and (possibly) storage- specialists following Sommer (1985). Possible Zn pollution was observed in two lakes (Oswego and Clear). Phytoplankton and sedimentary diatoms weakly correlated with sedimentary iron by comparison to Ni, V, or Zn. Few strong relationships were observed with manganese, copper, or cobalt. No statistically significant correlations were found with molybdenum, and few correlations between a conservative chemical parameter and a species of phytoplankton were found. There was poor correlation between trace metal concentrations and lake productivity, despite frequently observed correlations between individual species and particular trace metal fractions. These findings suggest that variations in absolute trace metal concentrations, and/or ratios, may be important factors for controlling species distribution, but have relatively little influence upon lake primary productivity or standing stocks.

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