title: Biomineralization of calcium carbonate in the cell wall of Lithothamnion crispatum (Hapalidiales, Rhodophyta): correlation between the organic matrix and the mineral phase.
abstract: Over the past few decades, progress has been made toward understanding the mechanisms of coralline algae mineralization. However, the relationship between the mineral phase and the organic matrix in coralline algae has not yet been thoroughly examined. The aim of this study was to describe the cell wall ultrastructure of Lithothamnion crispatum, a cosmopolitan rhodolith-forming coralline algal species collected near Salvador (Brazil), and examine the relationship between the organic matrix and the nucleation and growth/shape modulation of calcium carbonate crystals. A nanostructured pattern was observed in L. crispatum along the cell walls. At the nanoscale, the crystals from L. crispatum consisted of several single crystallites assembled and associated with organic material. The crystallites in the bulk of the cell wall had a high level of spatial organization. However, the crystals displayed cleavages in the (104) faces after ultrathin sectioning with a microtome. This organism is an important model for biomineralization studies as the crystallographic data do not fit in any of the general biomineralization processes described for other organisms. Biomineralization in L. crispatum is dependent on both the soluble and the insoluble organic matrix, which are involved in the control of mineral formation and organizational patterns through an organic matrix-mediated process. This knowledge concerning the mineral composition and organizational patterns of crystals within the cell walls should be taken into account in future studies of changing ocean conditions as they represent important factors influencing the physico-chemical interactions between rhodoliths and the environment in coralline reefs.
authors.affiliation: Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, CEP, 22460-030, Rio de Janeiro, Brazil.
authors.forename: Rodrigo Tomazetto
authors.initials: RT
authors.lastname: de Carvalho
authors.affiliation: Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, CEP, 22460-030, Rio de Janeiro, Brazil.
authors.forename: Leonardo Tavares
authors.initials: LT
authors.lastname: Salgado
authors.affiliation: Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, CEP, 22460-030, Rio de Janeiro, Brazil.
authors.forename: Gilberto Menezes
authors.initials: GM
authors.lastname: Amado Filho
authors.affiliation: Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, CEP, 22460-030, Rio de Janeiro, Brazil.
authors.forename: Rachel Nunes
authors.initials: RN
authors.lastname: Leal
authors.affiliation: Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, CEP, 21941-590, Rio de Janeiro, Brazil.
authors.forename: Jacques
authors.initials: J
authors.lastname: Werckmann
authors.affiliation: Centro Brasileiro de Pesquisas Físicas, CEP, 22290-180, Rio de Janeiro, Brazil.
authors.forename: André Linhares
authors.initials: AL
authors.lastname: Rossi
authors.affiliation: Instituto Nacional de Metrologia, Qualidade e Tecnologia, Diretoria de Metrologia Científica e Industrial, CEP, 25250-020, Duque de Caxias, Brazil.
authors.forename: Andrea Porto Carreiro
authors.initials: APC
authors.lastname: Campos
authors.affiliation: Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, CEP, 22460-030, Rio de Janeiro, Brazil.
authors.forename: Cláudia Santiago
authors.initials: CS
authors.lastname: Karez
authors.affiliation: Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, CEP, 21941-590, Rio de Janeiro, Brazil.
authors.forename: Marcos
authors.initials: M
authors.lastname: Farina
mesh_terms: D001938:Brazil; D002113:Calcification, Physiologic; D002119:Calcium Carbonate / Q000378:metabolism*; D002473:Cell Wall / Q000502:physiology / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D000461:Rhodophyta / Q000502:physiology*
chemical_list: D002119:Calcium Carbonate
keywords: 
  Lithothamnion crispatum
  ; biogenic calcium carbonate; biomineralization; calcareous algae; organic matrix; polysaccharides