Search results for "Euplectella"
showing 2 items of 2 documents
Bio-Sintering/Bio-Fusion of Silica in Sponge Spicules
2012
The synthesis of siliceous spicules in both demosponges and hexactinellids is enzymatically driven via silicatein. This enzyme exists both intra-spicularly and in the extra-spicular space. It catalyzes the formation of bio-silica constituting the silica lamellae that are formed during the appositional (layer-by-layer) growth of the spicules. The extent of (bio-silica forming) activity of silicatein from the demosponge Suberites domuncula measured in vitro reflects the amount of bio-silica required for the formation of spicules in vivo. It is shown that during growth and maturation of the spicules in demosponges a bio-fusion process occurs that results in an intra-spicular sintering of the s…
Silica-protein composite layers of the giant basal spicules from Monorhaphis: Basis for their mechanical stability
2010
The hexactinellid sponge Monorhaphis chuni possesses with its giant basal spicules the largest biosilica structure on Earth. The approximately 8.5-mm-thick spicules are composed of up to 800 lamellae. By application of high-resolution electron microscopy (HR-SEM), it is shown that within the siliceous lamellae a proteinaceous scaffold exists which is composed of one protein of a size of 27 kDa. Analyses with Fourier transform infrared (FT-IR) emission and energy-dispersive X-ray (EDX) spectroscopy support this localization of the protein. No evidence for the presence of protein on the surfaces of the lamellae could be obtained. Heating the giant basal spicule to 600 °C destroys and eliminat…