Towards the Chemical Analysis of Diatoms’ Silicon Storage Pools: A Differential Centrifugation-Based Separation Approach

Diatoms are unicellular algae and occur ubiquitously in almost every marine freshwater habitat on earth. They produce intricately structured cell walls, which mainly consist of amorphous silica. To synthesize their diatoms take up monosilicic acid from the environment store it. These silicon storage pools (SSPs) can exceed solubility silicic by one to two orders magnitude, as observed various diatom species. However, chemical composition cellular localization has not yet been elucidated. It is suggested that SSPs may stabilized aggregates such pre-condensed silica particles or silica-containing vesicles. Isolation protocols for without significant modification required prove hypotheses. A critical issue efficient separation components wall fragments artefacts, interfere with analytical methods targeting silicon. this end, a comparative study was performed exponentially grown cells extracted, purified walls (biosilica) observe sedimentation behavior after lysis. Cell cultures were lysed bead beating then fractionated differential centrifugation. The obtained fractions analyzed total content (tSi) using molybdenum blue assay (MBA) alkaline treatment. revealed absent above 1000 × g. Compared biosilica, significantly higher concentration found pellets centrifugation at moderately high forces. differences correspond few percent silicon, assumed be part SSPs. Only relatively low amounts silica/silicic remain supernatant centrifugal This indicates present larger sediment lower According Stokes’ law, only below ca. 25 nm radius would final supernatant. leads conclusion must and/or associated compartments/aggregates.