Benzerara Karim, Skouri-Panet Feriel, Li Jinhua, Férard Céline, Gugger Muriel, Laurent Thierry, Couradeau Estelle, Ragon Marie, Cosmidis Julie, Menguy Nicolas, Margaret-Oliver Isabel, Tavera Rosaluz, López-García Purificación, Moreira David
Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie, Sorbonne Universités, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7590, Université Pierre et Marie Curie Paris 06, Muséum National d'Histoire Naturelle, Institut de Recherche pour le Développement Unité Mixte de Recherche 206, 75005 Paris, France;
Collection des Cyanobactéries, Institut Pasteur, 75724 Paris Cedex 15, France;
Proc Natl Acad Sci U S A. 2014 Jul 29;111(30):10933-8. doi: 10.1073/pnas.1403510111. Epub 2014 Jul 9.
Cyanobacteria have played a significant role in the formation of past and modern carbonate deposits at the surface of the Earth using a biomineralization process that has been almost systematically considered induced and extracellular. Recently, a deep-branching cyanobacterial species, Candidatus Gloeomargarita lithophora, was reported to form intracellular amorphous Ca-rich carbonates. However, the significance and diversity of the cyanobacteria in which intracellular biomineralization occurs remain unknown. Here, we searched for intracellular Ca-carbonate inclusions in 68 cyanobacterial strains distributed throughout the phylogenetic tree of cyanobacteria. We discovered that diverse unicellular cyanobacterial taxa form intracellular amorphous Ca-carbonates with at least two different distribution patterns, suggesting the existence of at least two distinct mechanisms of biomineralization: (i) one with Ca-carbonate inclusions scattered within the cell cytoplasm such as in Ca. G. lithophora, and (ii) another one observed in strains belonging to the Thermosynechococcus elongatus BP-1 lineage, in which Ca-carbonate inclusions lie at the cell poles. This pattern seems to be linked with the nucleation of the inclusions at the septum of the cells, showing an intricate and original connection between cell division and biomineralization. These findings indicate that intracellular Ca-carbonate biomineralization by cyanobacteria has been overlooked by past studies and open new perspectives on the mechanisms and the evolutionary history of intra- and extracellular Ca-carbonate biomineralization by cyanobacteria.
蓝细菌在地球表面过去和现代碳酸盐沉积物的形成过程中发挥了重要作用，其生物矿化过程几乎一直被认为是诱导性的且发生在细胞外。最近，有报道称一种深分支蓝细菌物种——“候选石栖球囊蓝细菌（Candidatus Gloeomargarita lithophora）”能形成细胞内富含钙的无定形碳酸盐。然而，发生细胞内生物矿化的蓝细菌的重要性和多样性仍然未知。在此，我们在分布于蓝细菌系统发育树中的68个蓝细菌菌株中寻找细胞内碳酸钙内含物。我们发现，多种单细胞蓝细菌类群形成细胞内无定形碳酸钙，且具有至少两种不同的分布模式，这表明至少存在两种不同的生物矿化机制：（i）一种是碳酸钙内含物分散在细胞质中，如在“候选石栖球囊蓝细菌”中；（ii）另一种在属于嗜热栖热菌BP - 1谱系的菌株中观察到，其中碳酸钙内含物位于细胞两极。这种模式似乎与内含物在细胞隔膜处的成核有关，显示出细胞分裂与生物矿化之间复杂而独特的联系。这些发现表明，过去的研究忽略了蓝细菌的细胞内碳酸钙生物矿化现象，并为蓝细菌细胞内和细胞外碳酸钙生物矿化的机制及进化历史开辟了新的视角。
