Control of aragonite deposition in colonial corals by intra-skeletal macromolecules

Giuseppe Falini, Michela Reggi, Simona Fermani, Francesca Sparla, Stefano Goffredo, Zvy Dubinsky, Oren Levi, Yannicke Dauphin, Jean Pierre Cuif

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47 Scopus citations

Abstract

Scleractinian coral skeletons are composed mainly of aragonite in which a small percentage of organic matrix (OM) molecules is entrapped. It is well known that in corals the mineral deposition occurs in a biological confined nucleation site, but it is still unclear to what extent the calcification is controlled by OM molecules. Hence, the shape, size and organization of skeletal crystals from the fiber level through the colony architecture, were also attributed to factors as diverse as nucleation site mineral supersaturation and environmental factors in the habitat. In this work the OMs were extracted from the skeleton of three colonial corals, Acropora digitifera, Lophelia pertusa and Montipora caliculata. A. digitifera has a higher calcification rate than the other two species. OM molecules were characterized and their CaCO3 mineralization activity was evaluated by experiments of overgrowth on coral skeletons and of precipitation from solutions containing OM soluble and insoluble fractions and magnesium ions. The precipitates were characterized by spectroscopic and microscopic techniques. The results showed that the OM molecules of the three coral share similar features, but differ from those associated with mollusk shells. However, A. digitifera OM shows peculiarities from those from L. pertusa and M. caliculata. The CaCO3 overgrowth and precipitation experiments confirm the singularity of A. digitifera OM molecules as mineralizers. Moreover, their comparison indicates that only specific molecules are involved in the polymorphism control and suggests that when the whole extracted materials are used the OM's main effect is on the control of particles' shape and morphology.

Original languageEnglish
Pages (from-to)226-238
Number of pages13
JournalJournal of Structural Biology
Volume183
Issue number2
DOIs
StatePublished - Aug 2013

Bibliographical note

Funding Information:
The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement n° [249930 – CoralWarm: Corals and global warming: the Mediterranean versus the Red Sea]. GF and SF thank the Consorzio Interuniversitario di Ricerca della Chimica dei Metalli nei Sistemi Biologici (CIRC MSB) for the support.

Keywords

  • Biomineralization
  • Calcium carbonate precipitation
  • Corals
  • Magnesium ions
  • Organic matrix

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