In situ electron microscopy characterization of intracellular ion pools in mineral forming microalgae

Yuval Kadan, Lior Aram, Eyal Shimoni, Smadar Levin-Zaidman, Shilo Rosenwasser, Assaf Gal*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


The formation of coccoliths, intricate calcium carbonate scales that cover the cells of unicellular marine microalgae, is a highly regulated biological process. For decades, scientists have tried to elucidate the cellular, chemical, and structural mechanisms that control the precise mineralogy and shape of the inorganic crystals. Transmission electron microscopy was pivotal in characterizing some of the organelles that orchestrate this process. However, due to the difficulties in preserving soluble inorganic phases during sample preparation, only recently, new intracellular ion-pools were detected using state-of-the-art cryo X-ray and electron microscopy techniques. Here, we combine a completely non-aqueous sample preparation procedure and room temperature electron microscopy, to investigate the presence, cellular location, and composition, of mineral phases inside mineral forming microalga species. This methodology, which fully preserves the forming coccoliths and the recently identified Ca-P-rich bodies, allowed us to identify a new class of ion-rich compartments that have complex internal structure. In addition, we show that when carefully choosing heavy metal stains, elemental analysis of the mineral phases can give accurate chemical signatures of the inorganic phases. Applying this approach to mineral forming microalgae will bridge the gap between the low-preservation power for inorganic phases of conventional chemical-fixation based electron microscopy, and the low-yield of advanced cryo techniques.

Original languageAmerican English
Article number107465
JournalJournal of Structural Biology
Issue number1
StatePublished - 1 Apr 2020

Bibliographical note

Publisher Copyright:
© 2020 Elsevier Inc.


  • Biomineralization
  • Coccolith
  • Crystal growth
  • Diatom
  • Freeze-substitution


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