Cyanobacterium Creates Uncommon Carbonate | Chemical & Engineering News
Volume 90 Issue 18 | p. 35 | Concentrates
Issue Date: April 30, 2012

Cyanobacterium Creates Uncommon Carbonate

Species makes mineral containing magnesium, calcium, strontium, and barium internally?
Department: Science & Technology
News Channels: Biological SCENE
Keywords: cyanobacteria, mineral, calcification, carbonate, calcite, benstonite, Gloeomargarita
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A newly identified cyanobacterium contains white globules of a unique amorphous mineral.
Credit: Karim Benzerara/CNRS
White globules in a stringy grey tube, shown against a swiss-cheese-patterned substrate.
 
A newly identified cyanobacterium contains white globules of a unique amorphous mineral.
Credit: Karim Benzerara/CNRS

A newly identified cyanobacterium species produces within its cell an unusual amorphous carbonate mineral containing magnesium, calcium, strontium, and barium (Science, DOI: 10.1126/science.1216171). Cyanobacteria commonly produce extracellular carbonates, driven by export of photosynthesis by-product CO32–, but intracellular mineral formation is unusual in bacteria and has not been observed previously in cyanobacteria. A team led by Karim Benzerara and Purificación López-García of France’s National Center for Scientific Research (CNRS) discovered the new species, christened Candidatus Gloeomargarita lithophora, on rock samples taken from an alkaline lake in Mexico. The single-celled organisms are shaped like rods and are about 3.9 µm long and 1.1 µm wide. They contain granules about 0.27 µm wide of an amorphous mineral with the formula (SrBa2.7Mg1.4Ca0.9)Ca6Mg(CO3)13. The researchers propose that the granules may provide an alternative sink for CO32– and note that the cells may have to actively import Sr2+ and Ba2+ to make the mineral. The granules occupy about 6% of each cell’s volume and would increase cell density by 12%, perhaps adding weight to help the organisms stay put, so they can live on rocks or sediments, the authors say.

 
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Comments
Stanton de Riel (October 18, 2018 11:12 PM)
It's difficult to accept that an amorphous material with such a complex stoichiometry represents a single material -- more likely that the cyanobacteria simply dump carbonate with whatever divalent cations they have handy? Perhaps they would grow nicely in altered media, with correspondingly different deposited mineral composition?

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