X-ray nanotomography of coccolithophores reveals that coccolith mass and segment number correlate with grid size

• Published in: Nature communications Vol. 10; no. 1; p. 751
• Main Authors: Beuvier, T, Probert, I, Beaufort, L, Suchéras-Marx, B, Chushkin, Y, Zontone, F, Gibaud, A
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 14.02.2019; Nature Publishing Group UK; Nature Portfolio
• Subjects: Acidification; Base plates; Calcification; Calcite; Calcium carbonate; Correlation; Crystals; Earth Sciences; Image segmentation; Life Sciences; Microbiology and Parasitology; Microscopy; Nucleation; Nuclei (cytology); Oceanography; Sciences of the Universe; Seawater; X ray imagery; X-ray diffraction; Marine biology; Biomaterials
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-08635-x

Coccolithophores of the Noëlaerhabdaceae family are covered by imbricated coccoliths, each composed of multiple calcite crystals radially distributed around the periphery of a grid. The factors that determine coccolith size remain obscure. Here, we used synchrotron-based three-dimensional Coherent X-ray Diffraction Imaging to study coccoliths of 7 species of Gephyrocapsa, Emiliania and Reticulofenestra with a resolution close to 30 nm. Segmentation of 45 coccoliths revealed remarkable size, mass and segment number variations, even within single coccospheres. In particular, we observed that coccolith mass correlates with grid perimeter which scales linearly with crystal number. Our results indirectly support the idea that coccolith mass is determined in the coccolith vesicle by the size of the organic base plate scale (OBPS) around which R-unit nucleation occurs every 110-120 nm. The curvation of coccoliths allows inference of a positive correlation between cell nucleus, OBPS and coccolith sizes.