An intimate view into the silica deposition vesicles of diatoms

Abstract

Diatoms are single-celled microalgae that produce silica-based cell walls with intricate nano- and micropatterns. Biogenesis of diatom biosilica is a bottom-up process that occurs in large intracellular compartments termed silica deposition vesicles (SDVs). Investigating the mechanism of silica morphogenesis has so far been severely limited by the lack of methods for imaging the entire volume of an SDV with high spatial resolution during all stages of development. Here we have developed a method that allows for rapid identification and electron microscopy imaging of many different, full sized SDVs that are in the process of producing biosilica valves. This enabled visualizing the development of characteristic morphological biosilica features with unprecedented spatio-temporal resolution. During early to mid-term development, valve SDVs contained ~20 nm sized particles that were primarily associated with the radially expanding rib-like biosilica structures. The results from electron dispersive X-ray analysis suggests that the immature biosilica patterns are silica-organic composites. This supports the hypothesis that silica morphogenesis is dependent on organic biomolecules inside the SDV lumen.

Computational analysis of the effects of nitrogen source and sin1 knockout on biosilica morphology in the model diatom Thalassiosira pseudonana

“…Type 1 skeletons extracted from low-contrast images are typically fragmented. However, it is known that during valve formation, the ridges develop as a continuous branched network, with cross-connections between branches appearing at later stages of development [36,37]. To recover this continuous branching structure, we developed a second approach, designed to extract a connected (i.e.…”

“…T. pseudonana (clone CCMP 1335) was grown at 18 °C with a 16 h light/8 h dark cycle at 5000-10,000 lx, in artificial seawater (ASW) [37] lacking the nitrogen source. Sterile filtered NH 4 Cl or KNO 3 was added to a final concentration of 550 µM.…”

Computational Analysis of The Effects of Nitrogen Source and Sin1 Knockout on Biosilica Morphology in The Model Diatom Thalassiosira Pseudonana

“…Type 1 skeletons extracted from low-contrast images are typically fragmented. However, it is known that during valve formation, the ridges develop as a continuous branched network, with cross-connections between branches appearing at later stages of development [34,35]. To recover this continuous branching structure, we developed a second approach, designed to extract a connected (i.e.…”

“…T. pseudonana (clone CCMP 1335) was grown at 18 °C with a 16 h light/8 h dark cycle at 5000-10,000 lux, in artificial seawater (ASW) [35] lacking the nitrogen source. Sterile filtered NH4Cl or KNO3 was added to a final concentration of 550 µM.…”

A Biomimetic Peptide has no Effect on the Isotopic Fractionation during in Vitro Silica Precipitation

“…Biomineralisation occurs within the SDV through polymerisation 8 . The SDV contains genetically-encoded 9 , species-specific biomolecules that are thought to support and direct silica biosynthesis, and which are found intimately associated with the mature frustule. These biomolecules are represented as geometric shapes in Figure 1 and include long-chain polyamines 10 , as well as the different peptides known as silaffins, silacidins and frustulins [11][12][13] .…”