Some Structural and Functional Properties of a Possible Organic Matrix from the Frustules of the Freshwater Diatom <i>Cyclotella meneghiniana</i>

Swift, Debbie M.; Wheeler, A. P.

doi:10.1021/bk-1991-0444.ch024

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“…Clonal cultures of algae are widely used in laboratory experiments and have contributed greatly to our knowledge of microbial ecosystems (Thessen et al 2009). Among the multitude of diatom species, Gomphonema parvulum and Cyclotella meneghiniana represent the most widely distributed species (Swift and Wheeler 1991;Rimet et al 2009), both G. parvulum and C. meneghiniana have been frequently observed as dominant species in eutrophic water bodies (Finlay et al 2002;Rimet et al 2009;Pei et al 2010), C. meneghiniana has even been studied as a structure template in material science (Lenoci and Camp 2008). Because many physiological characteristics vary drastically among different species, Nitzschia sp., G. parvulum, and C. meneghiniana, all dominants in Chinese water bodies were chosen as representatives to investigate the effect of ammonia on photosystem and O 2 evolving reaction of freshwater diatoms.…”

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confidence: 99%

Effects of different nitrogen species on sensitivity and photosynthetic stress of three common freshwater diatoms

Zhang

Zhu

et al. 2012

Aquat Ecol

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Different sources of nitrogen pose diverse effects to algal community, but the mechanism of inhibitory effects of nitrogen sources on freshwater diatoms is not fully understood. The purpose of this study was to compare biomass, photosynthetic activity, and morphological structure of three common freshwater diatoms (Cyclotella meneghiniana, Nitzschia sp., and Gomphonema parvulum) under different nitrogen sources (NO 3 -or NH 4 ?). The sorption characteristic of each diatom was investigated, and chlorophyll a (Chl-a) content and oxygen evolution rate were analyzed to investigate stress of different nitrogen sources on each diatom in the batch experiments. Ammonium lowered the growth rate of C. meneghiniana and Nitzschia sp.when it was supplied in addition to growth-saturating nitrate concentrations, suggesting a combined effect of inhibition of nitrate uptake and direct ammonium stress. Oxygen evolution rate of Nitzschia sp. showed that the direct ammonium stress on the photosynthetic activity can be alleviated by coexistence of nitrate in the nitrogen enriched treatment, but not for C. meneghiniana and G. parvulum, which may be caused by a different nitrate transporter system within algal cells. Transmission electron microscopy was used to assess the toxicity of ammonium on ultrastructural chloroplast of each diatom. Ultrastructural changes in chloroplasts showed undefined electron-dense granules and lipid droplets, but the membrane integrity of cell was maintained, suggesting an adaptation to adjustment to ammonia stress. Results showed that Cyclotella meneghiniana and Nitzschia sp. were more sensitive to ammonium stress than Gomphonema parvulum on growth, but the mechanism remains unclear.

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Section: Introductionmentioning

confidence: 99%

Effects of different nitrogen species on sensitivity and photosynthetic stress of three common freshwater diatoms

Zhang

Zhu

et al. 2012

Aquat Ecol

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EVIDENCE OF AN ORGANIC MATRIX FROM DIATOM BIOSILICA¹

Swift

Wheeler

1992

Journal of Phycology

120

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Most biominerals appear to be composites of organic material and mineral. Whether biosilica is such a composite is unresolved because of a lack of evidence for such organic components. We present evidence that organic material exists within diatom biosilica and can be extracted using HF/NH4F solutions from frustules isolated from Cyclotella meneghiniana Kütz and diatomaceous earth. To eliminate organic casing on the silicified frustules as a source of organic materials, the casing was removed by oxidation of frustules with NaOCl before extraction. The removal of the casing was confirmed in that oxidized frustules no longer displayed the ability to be stained with ruthenium red and fluorescamine. Frustules examined with EDXA showed an emission peak from sulfur before treatment but no peak following treatment, indicating that oxidation removed organic sulfur. The organic material obtained from extracts of fresh frustules contained both soluble and insoluble components. Only soluble material was evident in extracts from diatomaceous earth. The soluble material appears to contain glycoproteins with relatively high levels of serine and glycine. The soluble proteins from fresh frustules also appear to be phosphorylated. Indirect evidence is presented that suggests the soluble proteins may contain regions of primary structure enriched in anionic amino acids. The soluble extracts differ from general cell contents when the two fractions are compared, suggesting that frustules contain specialized organic material. The identification of silica‐specific organic material suggests that mineralization in diatoms may be in part matrix‐mediated.

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Some Structural and Functional Properties of a Possible Organic Matrix from the Frustules of the Freshwater Diatom Cyclotella meneghiniana

Cited by 2 publications

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Effects of different nitrogen species on sensitivity and photosynthetic stress of three common freshwater diatoms

Effects of different nitrogen species on sensitivity and photosynthetic stress of three common freshwater diatoms

EVIDENCE OF AN ORGANIC MATRIX FROM DIATOM BIOSILICA¹

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Some Structural and Functional Properties of a Possible Organic Matrix from the Frustules of the Freshwater Diatom Cyclotella meneghiniana

Cited by 2 publications

References 0 publications

Effects of different nitrogen species on sensitivity and photosynthetic stress of three common freshwater diatoms

Effects of different nitrogen species on sensitivity and photosynthetic stress of three common freshwater diatoms

EVIDENCE OF AN ORGANIC MATRIX FROM DIATOM BIOSILICA1

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EVIDENCE OF AN ORGANIC MATRIX FROM DIATOM BIOSILICA¹