Engineering Diatoms with Novel Inorganic Material Compositions and Properties

Diatoms are a broad class of marine or freshwater single-cell eukaryotic algae that produce intricate nano-patterned silica-based cell walls under genetic control and under benign environmental conditions. These aspects make them a prime target for the development of new routes to synthesize bio-sourced materials with tunable hierarchal structures and properties. An exciting goal is to establish, understand, and engineer the biochemical processes of diatoms to produce functional inorganic materials with non-silica components, including the incorporation of diverse functional organic or metal oxide moieties. More specifically, advances in the genetics and molecular biology of diatoms are elucidating the intricacies of the pathways by which silica biosynthesis occurs under different environmental conditions.These are leading to design rules that will enable the biosynthesis machinery of diatoms to be modified to incorporate and control the amounts and placement of organosilica moieties, such as amines, saccharides, or alkenes, in functionalized nano-patterned biosilica products.Based on insights we have acquired into biosilicification pathways, we will develop genetic engineering approaches to substitute silicon atoms for other elements such as aluminum, boron, phosphorus, and gallium in bio-derived mixed oxide materials. Such materials are expected to exhibit novel adsorption, reaction, mechanical, ion-conducting, or optoelectronic properties that are of interest to the Army. The types and locations of the “non-natural” moieties will be established by using state-of-the-art spectroscopic and microscopy techniques, in combination with insights obtained from genetic analyses. These tools open the possibility of modifying the structures and compositions of the diatom cell walls to create novel functional nanomaterials for a broad range of applications, including on-site production of structural solids or materials for energy conversion/storage, environmental remediation, etc.