Morphogenesis of silica microstructures in diatoms

Diatoms are single-cell organisms with a remarkable cell wall called the diatom frustule. The frustule is made of multi-scale micro- and nano-patterned silica. The cell wall's intricate structure has puzzled scientists for quite some time. While a lot has recently been learned about the synthetic pathways that produce silica, still little is known about how the distinct hierarchical structure of the frustule is formed.

In this work, we used confocal fluorescence microscopy to obtain high-quality 3-D images of fluorescently-labelled C. Granii diatom frustules, and precisely tracked the positions of their structural features. The associated 2D projection of the pattern has strong short range order typical of a 2D crystal, while also exhibiting novel long-range order where bond-orientations preferentially point to the center of the frustule.

Following the hypothesis that the frustule is formed on a scaffold of phase-separated protein droplets (Sumper, 2002), we use molecular dynamics simulations to model the emergence of micron-scale order. By introducing a novel interaction term that favors radiallly oriented bonds, we capture the characterisic structure of C. Granii, as well as the full range of diverse patterns observed in other centric diatoms.