title: An early-branching microbialite cyanobacterium forms intracellular carbonates.
abstract: Cyanobacteria have affected major geochemical cycles (carbon, nitrogen, and oxygen) on Earth for billions of years. In particular, they have played a major role in the formation of calcium carbonates (i.e., calcification), which has been considered to be an extracellular process. We identified a cyanobacterium in modern microbialites in Lake Alchichica (Mexico) that forms intracellular amorphous calcium-magnesium-strontium-barium carbonate inclusions about 270 nanometers in average diameter, revealing an unexplored pathway for calcification. Phylogenetic analyses place this cyanobacterium within the deeply divergent order Gloeobacterales. The chemical composition and structure of the intracellular precipitates suggest some level of cellular control on the biomineralization process. This discovery expands the diversity of organisms capable of forming amorphous calcium carbonates.
authors.affiliation: Institut de Minéralogie et de Physique de la Matière Condensée, CNRS UMR 7590, Université Pierre et Marie Curie, Paris, France.
authors.forename: Estelle
authors.initials: E
authors.lastname: Couradeau
authors.forename: Karim
authors.initials: K
authors.lastname: Benzerara
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Gérard
authors.forename: David
authors.initials: D
authors.lastname: Moreira
authors.forename: Sylvain
authors.initials: S
authors.lastname: Bernard
authors.forename: Gordon E
authors.initials: GE
authors.lastname: Brown
authors.forename: Purificación
authors.initials: P
authors.lastname: López-García
mesh_terms: D001464:Barium / Q000032:analysis; D001483:Base Sequence; D018441:Biofilms; D002113:Calcification, Physiologic; D002118:Calcium / Q000032:analysis; D002119:Calcium Carbonate / Q000032:analysis*; D002254:Carbonates / Q000032:analysis* / Q000378:metabolism; D011232:Chemical Precipitation; D000458:Cyanobacteria / Q000145:classification / Q000302:isolation & purification* / Q000502:physiology* / Q000648:ultrastructure; D005798:Genes, Bacterial; D020459:Genes, rRNA; D002479:Inclusion Bodies / Q000737:chemistry* / Q000648:ultrastructure*; D060106:Lakes / Q000382:microbiology*; D008274:Magnesium / Q000032:analysis; D008800:Mexico; D008969:Molecular Sequence Data; D010802:Phylogeny; D013324:Strontium / Q000032:analysis
chemical_list: D002254:Carbonates; D001464:Barium; D002119:Calcium Carbonate; D008274:Magnesium; D002118:Calcium; D013324:Strontium