Silicon Metabolism in Marine Diatoms

Marine diatoms harness dissolved silicic acid to construct intricate silica cell walls known as frustules. Uptake occurs via specialised membrane transporters that concentrate silicic acid within the cytoplasm. Inside the cell, silica is polymerised within membrane-bound silica deposition vesicles (SDVs), where organic macromolecules guide nanometre-scale patterning. Once assembly is complete, the silica elements are exocytosed and integrated into the existing frustule architecture. This process balances the demands of membrane homeostasis with rigid mineral formation and contributes substantially to global biogeochemical cycles. Diatom blooms sequester carbon through photosynthesis and enhance the biological pump by sinking silica-encrusted cells to depth. Variations in silicification influence grazer interactions and nutrient recycling, shaping marine food webs and the distribution of silica across ocean basins. Understanding silicon metabolism in diatoms unites molecular transport, cell biology and ecosystem-scale impacts with implications for climate regulation, nutrient dynamics and the design of bioinspired materials.

Research from Nature Portfolio

Recent studies have revealed the structural dynamics of silica exocytosis in living diatoms. High-resolution cryo-electron tomography and live-cell fluorescence techniques show that, during cell-wall extrusion, the distal membrane of the SDV detaches and disintegrates externally, while the proximal membrane transforms into the new plasma boundary. This overturns the assumption of membrane recycling, demonstrating a unique mechanism where surplus membrane is discarded rather than retrieved. In parallel, in vitro analyses of recombinant silicic acid transporters have clarified their function as sodium-coupled symporters with a 1:1 stoichiometry and micromolar affinity. Mutational studies highlight conserved amino acid motifs essential for substrate recognition, laying the groundwork for detailed biophysical characterisation of silicon uptake and its evolutionary conservation among silicifying organisms.

Silicon Metabolism in Marine Diatoms publication trend

The graph below shows the total number of articles in silicon metabolism in marine diatoms across all publications each year (not limited to Nature Index journals).

Technical terms

Silicic acid: The soluble monomeric form of silicon (H₄SiO₄) taken up by diatom transporters from seawater.

Silica deposition vesicle (SDV): A membrane-bound compartment in which polymerisation of silicic acid into structured biosilica occurs.

Frustule: The rigid, porous silica exoskeleton of a diatom, composed of two interlocking valves and associated girdle bands.

Exocytosis: The cellular process by which completed silica elements are expelled from the SDV to become part of the frustule.

SIT transporter: A membrane protein family (Silicic acid Transporter) that actively imports silicic acid into diatom cells, often as a Na⁺ symporter.

References

1. Exocytosis of the silicified cell wall of diatoms involves extensive membrane disintegration. Nature Communications (2023).
2. Hexagonal Patterns in Diatom Silica Form via a Directional Two‐Step Process. Advanced Science (2024).
3. A siliceous arms race in pelagic plankton. Proceedings of the National Academy of Sciences of the United States of America (2024).
4. Direct evidence of the molecular basis for biological silicon transport. Nature Communications (2016).