Search results for "diatoms"

Diatoms from thermal-sulphur waters of “Fiume Caldo” (North-western Sicily).

2007

The present study describes the taxonomic composition, richness and seasonal dynamics of the diatom community from thermal-sulphur waters of "Fiume Caldo" (Northwestern Sicily). The diatom flora of these waters consists of 64 taxa, showing similarities with thermal diatom communities from different geographical areas. Among the recorded taxa, Diadesmis confervacea Kütz. is a new record for Sicily. Seasonal changes in assemblage composition and richness have been recorded; the highest diversity values were observed during winter and spring, while during summer the diatom community consisted of a limited number of organisms whereas blue-green algae were quantitatively dominant. Inside the stu…

Localization and Characterization of Ferritin in Demospongiae: A Possible Role on Spiculogenesis

2014

Iron, as inorganic ion or as oxide, is widely used by biological systems in a myriad of biological functions (e.g., enzymatic, gene activation and/or regulation). In particular, marine organisms containing silica structures—diatoms and sponges—grow preferentially in the presence of iron. Using primary sponge cell culture from S. domuncula–primmorphs—as an in vitro model to study the Demospongiae spiculogenesis, we found the presence of agglomerates 50 nm in diameter exclusively inside sponge specialized cells called sclerocytes. A clear phase/material separation is observed between the agglomerates and the initial stages of intracellular spicule formation. STEM-HRTEM-EDX analysis of the agg…

Role of hexagonal structure-forming lipids in diadinoxanthin and violaxanthin solubilization and de-epoxidation

2005

In this study, we have examined the influence of different lipids on the solubility of the xanthophyll cycle pigments diadinoxanthin (Ddx) and violaxanthin (Vx) and on the efficiency of Ddx and Vx de-epoxidation by the enzymes Vx de-epoxidase (VDE) from wheat and Ddx de-epoxidase (DDE) from the diatom Cyclotella meneghiniana, respectively. Our results show that the lipids MGDG and PE are able to solubilize both xanthophyll cycle pigments in an aqueous medium. Substrate solubilization is essential for de-epoxidase activity, because in the absence of MGDG or PE Ddx and Vx are present in an aggregated form, with limited accessibility for DDE and VDE. Our results also show that the hexagonal st…

High yield recombinant production of a self-assembling polycationic peptide for silica biomineralization.

2015

We report the recombinant bacterial expression and purification at high yields of a polycationic oligopeptide, P5S3. The sequence of P5S3 was inspired by a diatom silaffin, a silica precipitating peptide. Like its native model, P5S3 exhibits silica biomineralizing activity, but furthermore has unusual self-assembling properties. P5S3 is efficiently expressed in Escherichia coli as fusion with ketosteroid isomerase (KSI), which causes deposition in inclusion bodies. After breaking the fusion by cyanogen bromide reaction, P5S3 was purified by cation exchange chromatography, taking advantage of the exceptionally high content of basic amino acids. The numerous cationic charges do not prevent, b…

Assessing past ecological changes in lake Isojärvi and its suitability as a Finnish lake reference site using sedimentary diatoms

2008

Effects of mechanical mixing on lake water quality, with special emphasis on under-ice phytoplankton

2015

Niche position drives interspecific variation in occupancy and abundance in a highly-connected lake system

2019

Highlights • We studied interspecific variation in occupancy and abundance of freshwater species. • Occupancy and abundance correlated positively for both diatoms and macroinvertebrates. • Niche position had clearest effects on variation in occupancy and abundance. • The more marginal the niche position, the rarer a species is. We examined how niche position, niche breadth, biological traits and taxonomic relatedness affect interspecific variation in occupancy and abundance of two commonly-used biological indicator groups, i.e. diatoms and macroinvertebrates. We studied 291 diatom and 103 macroinvertebrate species that occupied the littoral zones of a large (305 km2) highly-connected freshw…