The Evolution of Advanced Mechanical Defenses and Potential Technological Applications of Diatom Shells

Abstract

Diatoms are unicellular algae with silicified cell walls, which exhibit a high degree of symmetry and complexity. Their diversity is extraordinarily high; estimates suggest that about 10(5) marine and limnic species may exist. Recently, it was shown that diatom frustules are mechanically resilient, statically sophisticated structures made of a tough glass-like composite. Consequently, to break the frustules, predators have to generate large forces and invest large amounts of energy. In addition, they need feeding tools (e.g., mandibles or gastric mills) which are hard, tough, and resilient enough to resist high stress and wear, which are bound to occur when they feed on biomineralized objects such as diatoms or other biomineralized protists. Indeed, many copepods feeding on diatoms possess, in analogy to the enamelcoated teeth of mammals, amazingly complex, silica-laced mandibles. The highly developed adaptations both to protect and to break diatoms indicate that selection pressure is high to optimize material properties and the geometry of the shells to achieve mechanical strength of the overall structure. This paper discusses the mechanical challenges which force the development of mechanical defenses, and the structural components of the diatom frustules which indicate that evolutionary optimization has led to mechanically sophisticated structures. Understanding the diatom frustule from the nanometer scale up to the whole shell will provide new insights to advanced combinations of nanostructured composite ceramic materials and lightweight architecture for technological applications.

Use of Agent-Based Modeling To Explore the Mechanisms of Intracellular Phosphorus Heterogeneity in Cultured Phytoplankton

“…When a cell grows to twice the minimum, it divides and creates two daughter cells with approximately half the size (9,22). Diatoms have a silicate outer cell wall, called a frustule, which provides protection from predators (24). In many diatoms, the frustule makes the cell division process complex, because the daughter cell's valve forms inside the mother cell; therefore, it must have a smaller diameter (25).…”

Deformation Modes and Structural Response of Diatom Frustules

“…Hamm et al [6] investigated the potential of diatom frustules as armor against predators based on microneedle loading tests, discovering an inverse relation between frustule size and mechanical strength up to the point of fracture. The investigators further elaborated [17] on the relation between the structural components of the frustule and the mechanical loads that diatoms experience in their natural environment using both experiments and simulations. Almqvist et al…”

Diatomaceous Lessons in Nanotechnology and Advanced Materials

“…[10] There are recent reviews on diatom molecular biology, [11,12] biotechnology, [13] biomimetics, [14] and frustule formation. [15] This progress report focuses on the developments and potentials for diatom frustules as advanced materials by examining frustule structural features, [16] biomimetic synthesis of novel silica-based materials, chemical transformations, and templating techniques. Possible applications including new nanofabrication techniques, chemoand biosensing, particle sorting, and control of particles in micro-and nanofluidics will be highlighted.…”