Continuum modelling of structure formation of biosilica patterns in diatoms

Manfred Bobeth,Hagen Eckert,Rafael Gutierrez,Gianaurelio Cuniberti,David Werner,Hongliu Yang,Arezoo Dianat

doi:10.1186/s42833-020-00018-7

Abstract

Formation of regularly structured silica valves of various diatom species is a particularly fascinating phenomenon in biomineralization. Intensive investigations have been devoted to elucidate the formation mechanisms of diatom valve structures. Phase-separation of species-specific organic molecules has been proposed to be involved in pattern formation, where the evolving organic molecule structures serve as template for silica formation. In the present work, using a continuum approach, we investigate the conditions under which silica structures of high regularity can develop within a phase separation model. In relation to previously reported in vitro experiments of silica formation, which revealed the important role of phosphate ions in the self-assembly of organic molecules, we propose a model where phase separation is coupled with a chemical reaction. We analyze the impact of the reaction of phosphate ions with organic molecules on the appearing morphology of the organic template. Two- and three-dimensional simulations of the development of regular stationary patterns are presented. The influence of a confined geometry and an interaction of organic molecules with the walls on pattern formation is also addressed. We expect that our approach will be relevant for experimental studies aiming at inducing structure formation under controlled in vitro conditions.

Highlights

The formation of various beautiful silica structures of diatoms is a very fascinating example of biomineralization
To avoid the permanent coarsening of phase regions in conventional phase separation, we propose here a model where the phase separation is coupled with a chemical reaction [18], an approach which can be justified on the basis of the in vitro experiments of silica precipitation
The choice of long-chain polyamine (LCPA) as a reference organic component is motivated by their demonstrated influence on silica aggregation in vitro [20,21,22,23] as well as by their broad dispersion into the silica phase, shown recently in [24]. The latter fact suggests their relevance for the formation of the organic–inorganic interface under in vivo conditions. In view of these findings, we suggest that the reaction of organic molecules with phosphate ions has an important impact on the phase separation of the organic component and, it should be taken into account in the theoretical modeling of this process

Summary

Introduction

The formation of various beautiful silica structures of diatoms is a very fascinating example of biomineralization. Considerable progress has been made in elucidating the chemical and biological processes, which are involved in the silica morphogenesis of diatom valves (cf for example [1,2,3,4,5]). Only relatively few works have dealt with the very challenging theoretical modeling of the morphogenesis of diatom valves [8,9,10,11,12,13]. Bobeth et al BMC Mat (2020) 2:12 simulations, phase separation was influenced by an additional local field arising from the pre-existing silica costae within the base layer. Depending on the choice of this regular pre-patterning field, different highly symmetric valve structures could be achieved

Objectives

Conclusion