Werner Peter, Blumtritt Horst, Natalio Filipe
MPI of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany.
MPI of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany.
J Struct Biol. 2017 Jun;198(3):186-195. doi: 10.1016/j.jsb.2017.03.005. Epub 2017 Mar 18.
The skeletal system of Demospongiae consists of siliceous spicules, which are composed of an axial channel containing an organic axial filament (AF) surrounded by a compact layer of hydrated amorphous silica. Here we report the ultrastructural investigations of the AF of siliceous spicules from two Demospongiae: Suberites domuncula and Tethya aurantium. Electron microscopy, electron diffraction and elemental mapping analyses on both longitudinal and transversal cross-sections yield that spicules's AF consist of a three-dimensional crystal lattice of six-fold symmetry. Its structure, which is the result of a biological growth process, is a crystalline assembly characterized by a lattice of organic cages (periodicity in the range of 6nm) filled with enzymatically-produced silica. In general, the six-fold lattice symmetry is reflected by the morphology of the AF, which is characterized by six-fold facets. This seems to be the result of a lattice energy minimization process similar to the situation found during the growth of inorganic crystals. Our structural exploitation of three-dimensional organic lattices generated by biological systems is expected to contribute for explaining the relation between axial filament's ultrastructure and spicule's ultimate morphology.
寻常海绵纲的骨骼系统由硅质骨针组成，这些骨针由一个轴向通道构成，该通道包含一根有机轴向丝（AF），其周围是一层紧密的水合无定形二氧化硅。在此，我们报告了对两种寻常海绵纲动物——黄海绵（Suberites domuncula）和橙黄桶海绵（Tethya aurantium）硅质骨针轴向丝的超微结构研究。对纵向和横向横截面进行的电子显微镜、电子衍射和元素图谱分析表明，骨针的轴向丝由具有六重对称性的三维晶格组成。其结构是生物生长过程的结果，是一种晶体组装体，其特征是由充满酶促生成二氧化硅的有机笼状晶格（周期在6纳米范围内）构成。一般来说，轴向丝的形态反映了六重晶格对称性，其特征是具有六重面。这似乎是晶格能量最小化过程的结果，类似于在无机晶体生长过程中发现的情况。我们对生物系统产生的三维有机晶格的结构研究，有望有助于解释轴向丝超微结构与骨针最终形态之间的关系。
