An Early-Branching Microbialite Cyanobacterium Forms Intracellular Carbonates

Estelle Couradeau (1, 2) , Karim Benzerara (1) , Emmanuelle Gérard (2) , David Moreira (3) , Sylvain Bernard (4) , Gordon E. Brown , Purificación López-García (3)

1 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
2 IPGP - Institut de Physique du Globe de Paris
3 ESE - Ecologie Systématique et Evolution
4 LMCM - Laboratoire de Minéralogie et Cosmochimie du Muséum

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.

Mots clés: GEOCHEM PHYS

Domaines: Planète et Univers [physics]

Estelle Couradeau, Karim Benzerara, Emmanuelle Gérard, David Moreira, Sylvain Bernard, et al.. An Early-Branching Microbialite Cyanobacterium Forms Intracellular Carbonates. Science, 2012, 336, pp.459. ⟨10.1126/science.1216171⟩. ⟨insu-03583352⟩