Marine Biotechnology

, Volume 20, Issue 3, pp 304–312 | Cite as

Involvement of Acidic Polysaccharide Ph-PS-2 and Protein in Initiation of Coccolith Mineralization, as Demonstrated by In Vitro Calcification on the Base Plate

  • Shunto Sakurada
  • Shoko Fujiwara
  • Michio Suzuki
  • Toshihiro Kogure
  • Tatsuya Uchida
  • Tomonari Umemura
  • Mikio Tsuzuki
Original Article


Coccolithophorids, unicellular marine microalgae, have calcified scales with elaborate structures, called coccoliths, on the cell surface. Coccoliths generally comprise a base plate, CaCO3, and a crystal coat consisting of acidic polysaccharides. In this study, the in vitro calcification conditions on the base plate of Pleurochrysis haptonemofera were examined to determine the functions of the base plate and acidic polysaccharides (Ph-PS-1, -2, and -3). When EDTA-treated coccoliths (acidic polysaccharide-free base plates) or low pH-treated coccoliths (whole acidic polysaccharide-containing base plates) were used, mineralization was not detected on the base plate. In contrast, in the case of coccoliths which were decalcified by lowering of the pH and then treated with urea (Ph-PS-2-containing base plates), distinct aggregates, probably containing CaCO3, were observed only on the rim of the base plates. Energy dispersive X-ray spectroscopy (EDS) confirmed that the aggregates contained Ca and O, although X-ray diffraction analysis did not reveal any evidence of crystalline materials. Also, in vitro mineralization experiments performed on EDTA-treated coccoliths using isolated acidic polysaccharides demonstrated that the Ca-containing aggregates were markedly formed only in the presence of Ph-PS-2. Furthermore, in vitro mineralization experiments conducted on protein-extracted base plates suggested that the coccolith-associated protein(s) are involved in the Ca deposition. These findings suggest that Ph-PS-2 associated with the protein(s) on the base plate rim initiates Ca2+ binding at the beginning of coccolith formation, and some other factors are required for subsequent calcite formation.


Acidic polysaccharide Calcification Calcium Coccolithophorid Pleurochrysis haptonemofera Urea-extraction 



We are grateful to Dr. I. Inouye of Tsukuba University for kindly providing the P. haptonemofera cells, to Drs. Y. Hirokawa of Tokyo University of Pharmacy and M. Kawachi of NIES for the excellent scanning electron micrographs of the cells and hearty encouragement, and to Mr. N. J. Halewood for correcting the English version of this paper.

Funding Information

This work was supported by a Grant-in-Aid from the Ministry of Education, Science, Sports and Culture, Japan (16 K07427), and the Promotion and Mutual Aid Corporation for Private Schools.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • Shunto Sakurada
    • 1
  • Shoko Fujiwara
    • 1
  • Michio Suzuki
    • 2
  • Toshihiro Kogure
    • 3
  • Tatsuya Uchida
    • 1
  • Tomonari Umemura
    • 1
  • Mikio Tsuzuki
    • 1
  1. 1.School of Life SciencesTokyo University of Pharmacy and Life SciencesHachiojiJapan
  2. 2.Department of Applied Biological Chemistry, Graduate School of Agricultural and Life SciencesThe University of TokyoTokyoJapan
  3. 3.Department of Earth and Planetary Science, Graduate School of ScienceThe University of TokyoTokyoJapan

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