Structural evidence for extracellular silica formation by diatoms

Area of Science:

• Biomineralization
• Microbiology
• Marine Biology

Background:

• Diatoms are unicellular microalgae known for their intricate silica cell walls.
• Silicification, the process of silica formation, was traditionally believed to occur exclusively within intracellular silica deposition vesicles.
• Diatom cell wall morphogenesis involves precise biological control over mineral sculpting.

Purpose of the Study:

• To investigate the formation mechanism of long silicified extensions in diatoms.
• To challenge the prevailing paradigm of intracellular diatom silicification.
• To understand the environmental factors influencing silica structure formation.

Main Methods:

• Cryo-electron tomography was employed for in situ, 3D imaging of silica formation at nanometer resolution.
• Observation of silica formation under varying silicon concentrations.
• Comparative analysis of silicification in different diatom structures.

Main Results:

• Contrary to the established paradigm, long silicified extensions were observed to form extracellularly, outside the cytoplasm.
• The formation of these specific silica extensions was inhibited at low silicon concentrations.
• These findings suggest a distinct silicification mechanism for these structures compared to other cell wall elements.

Conclusions:

• Diatoms utilize unconventional extracellular strategies for forming certain silica structures.
• This discovery expands the known repertoire of diatom silicification mechanisms.
• Further research is needed to elucidate the precise biochemical pathways involved in extracellular silica deposition.