Diatom Silicification

Diatoms are the most abundant microalgae group, inhibiting almost every ecological niche on earth. From fresh water lakes and streams to the open ocean, these unicellular photosynthetic organisms show remarkable ability to adapt to various environmental conditions.

The hallmark of diatoms is their ability to produce cell wall coverage made of silicon dioxide. Silica formation is an intracellular process regulated by the cell cycle. Silicic acid molecules, the bioavailable source for silica in the aquatic environment, are taken up by the cell, and then converted by an enigmatic process to the convoluted shape of the mature cell wall. Silica deposition occurs inside a specialized organelle, and is controlled by the orchestrated activity of macromolecules.

Several proteins were isolated and characterized from the cell wall silica of few diatom species. However, their functional role during silica formation is not clear. One possible function is to catalyse the condensation of the monomeric silica units into the mature mineral, other possibilities include morphogenesis and shape control of the mineral phase, as well as intracellular transport of the building blocks.

Our goal is to acquire a mechanistic understanding of the sequence of events underlying diatom silicification by applying a range of techniques, from high resolution electron microscopy and tomography to the chemical elucidation of the intermediate phases that participate in silica formation.

Cell walls of the diatom Thalassiosira pseudonana