title: Lattice distortions in coccolith calcite crystals originate from occlusion of biomacromolecules.
abstract: During biomineralization, organisms control the formation and morphology of a mineral using biomacromolecules. The biomacromolecules that most strongly interact with the growing crystals frequently get occluded within. Such an observation has been recently obtained for the calcium carbonate producing coccolithophore species Pleurochrysis carterae. Coccolithophores are unicellular algae that produce calcified scales built from complex-shaped calcite crystals, termed coccoliths. It is unclear how widespread the phenomenon of biomacromolecular occlusion within calcite crystals is in calcifying haptophytes such as coccolithophores. Here, the coccoliths of biological replicates of the bloom forming Emiliania huxleyi are compared with that of Pleurochrysis carterae, two species with different coccolith morphologies and crystal growth mechanisms. From high-resolution synchrotron X-ray diffraction, changes in the lattice parameters of coccolith calcite, after heating to 450°C, are observed and associated with macrostrain originating from occluded biomacromolecules. We propose a mechanism governing the biomacromolecules' interaction with the growing coccolith crystals and their likely origin.
authors.affiliation: Max-Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany; Max-Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany. Electronic address: matthew.hood@mpikg.mpg.de.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Hood
authors.affiliation: Max-Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
authors.forename: Hanna
authors.initials: H
authors.lastname: Leemreize
authors.affiliation: Max-Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany.
authors.forename: André
authors.initials: A
authors.lastname: Scheffel
authors.affiliation: Max-Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany. Electronic address: damien.faivre@mpikg.mpg.de.
authors.forename: Damien
authors.initials: D
authors.lastname: Faivre
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry*; D003460:Crystallization; D058087:Haptophyta / Q000737:chemistry*; D046912:Multiprotein Complexes / Q000737:chemistry; D013045:Species Specificity; D014961:X-Ray Diffraction
chemical_list: D046912:Multiprotein Complexes; D002119:Calcium Carbonate
keywords: Biogenic crystal growth; Biomineralization; Calcium carbonate; Coccoliths; High-resolution X-ray diffraction