Silica Processing by Diatoms

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The overarching goal of the present project is the understanding of the intracellular state and stabilization of silicic acid after its uptake by diatoms from their environment. Preliminary work consistently revealed the presence of significant amounts of silicon-bearing species/ silica precursors stabilized in the cell interior as Silicon Storage Pools (SSPs) before cell wall formation takes place inside the Silicon Deposition Vesicle (SDV). Various hypotheses for intracellular stabilization mechanisms exist. In the first project period, we will thus focus on the chemical characterization of SSPs. We will study how SSPs depend on growth conditions and on the cell cycle. The extraction and fractionation steps of SSP-containing material will first rely on centrifugation approaches. It is, furthermore, envisioned to elucidate the Si-content of SSPs using techniques like silicomolybdic acid assay and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The obtained Si-containing samples will be subject to further analysis by 29Si NMR spectroscopy and Mass Spectrometry (MS). The stabilization of SSPs by long-chain polyamines (LCPAs) or LCPA-modified proteins is hypothesized and will be tested using MS in combination with advanced solid-state NMR methods and optical spectroscopy (IR/Raman).