Diatoms deposit silicon into intracellular membrane-enclosed silicon deposition vesicles (SDVs). In SDVs, long chain polyamines and silaffin proteins aid in the concentration and formation of silica polymers. Subsequently these are deposited at the cell surface, forming the intricate silica frustule. Right: We propose to use silicalemma-associated proteins (SAPs) to target transporter proteins or enzymes to silica deposition vesicles, with the overarching goal that the transporter/enzyme in question will ensure the uptake of an interesting ion/molecule into the SDV and silica frustule.
This project seeks to use a combination of microbiology, biochemistry and forefront sequencing technologies to elucidate the molecular mechanisms underlying the biosilicification processes in a range of diatoms sourced from both freshwater and marine environments. Specifically, we seek to understand how morphologically related diatoms in different environments regulate their biosilicification process, as it is known that e.g., freshwater diatoms appear to produce an order of magnitude more silica per cell than their marine morphological relatives . The outcome of this project will not only greatly add to our general understanding of diatom physiology but will provide tools to tap into and ultimately modify the biosilicification process of diatoms using genetic engineering and synthetic biology, essentially converting them to ‘microbial cell factories’ for the production of silica-based materials.
The overarching goals of this project are to establish, understand, and repurpose the silicification pathways of diatoms to engineer materials with novel properties. Our primary objectives are focused on determining the genetic differences between freshwater and marine diatoms, their respective silicification mechanisms that underlie changes in silica patterning, deposition rates, and morphology in response to environmental factors. Of particular interest are the genetic responses and morphological consequences when diatoms are denied adequate silicon. During the current review period we have concentrated on:
identifying and cultivating morphologically-related pairs of freshwater and marine diatoms in batch cultures, for extraction of DNA for genome sequencing,
cultivating morphologically-related pairs of freshwater and marine diatoms in a chemostat, under strictly controlled nutrient conditions, and
developing methods for extracting high-quality DNA for genome sequencing; and RNA for transcriptomic analyses of gene expression patterns in freshwater and marine diatoms.
Our pursuits are aimed at developing new types of living materials with novel architectures, patterns, compositions, and length scales that are useful for structural, opto-electronic, and biomaterials applications relevant to the Army.