23 research outputs found
A role for the cell-wall protein silacidin in cell size of the diatom Thalassiosira pseudonana
Diatoms contribute 20% of global primary production and form the basis of many marine food webs. Although their species diversity correlates with broad diversity in cell size, there is also an intraspecific cell-size plasticity due to sexual reproduction and varying environmental conditions. However, despite the ecological significance of the diatom cell size for food-web structure and global biogeochemical cycles, our knowledge about genes underpinning the size of diatom cells remains elusive. Here, a combination of reverse genetics, experimental evolution and comparative RNA8 sequencing analyses enabled us to identify a previously unknown genetic control of cell size in the diatom Thalassiosira pseudonana. In particular, the targeted deregulation of the expression of the cell-wall protein silacidin caused a significant increase in valve diameter. Remarkably, the natural downregulation of the silacidin gene transcript due to experimental evolution under low temperature also correlated with cell-size increase. Our data give first evidence for a genetically controlled regulation of cell size in Thalassiosira pseudonana and possibly other centric diatoms as they also encode the silacidin gene in their genomes
Multimodality Imaging for Evaluation of Bicaval Valved Stent Implantation in Severe Tricuspid Regurgitation.
Preprocedural planning and postprocedural evaluation after transcatheter treatment of severe tricuspid regurgitation remain challenging and require further research and standardization. We illustrate the use of multimodality imaging techniques in 3 patients undergoing implantation of a novel custom-made bicaval valved stent for symptomatic treatment of severe tricuspid regurgitation. (Level of Difficulty: Advanced.)
Gold Nanoparticle-Decorated Diatom Biosilica: A Favorable Catalyst for the Oxidation of dâGlucose
Diatoms are unicellular
algae of enormous biodiversity that occur in all water habitats on
earth. Their cell walls are composed of amorphous biosilica and exhibit
species-specific nanoporous to microporous and macroporous patterning.
Therefore, diatom biosilica is a promising renewable material for
various applications, such as in catalysis, drug-delivery systems,
and biophotonics. In this study, diatom biosilica of three different
species (Stephanopyxis turris, Eucampia zodiacus, and Thalassiosira
pseudonana) was used as support material for gold
nanoparticles using a covalent coupling method. The resulting catalysts
were applied for the oxidation of d-glucose to d-gluconic acid. Because of its high specific surface area, well-established
transport pores, and the presence of small, homogeneously distributed
gold nanoparticles on the surface, diatom biosilica provides a highly
catalytically active surface and advanced accessibility to the active
sites. In comparison to those of the used reference supports, higher
catalytic activities (up to 3.28 Ă 10<sup>â4</sup> mmol<sub>Glc</sub> s<sup>â1</sup> mg<sub>Au</sub><sup>â1</sup> for T. pseudonana biosilica) and
slower deactivation were observed for two of the diatom biosilica
materials. In addition, diatom biosilica showed very high gold-loading
capacities (up to 45 wt %), with a homogeneous nanoparticle distribution