Scientists have discovered a species of cyanobacteria that makes tiny calcified structures inside its cells. Related microbes calcify on the outside.
Scientists have discovered skeletons in the cyanobacterial closet. A never-before-seen species of cyanobacterium loads its cells with little bonelike lumps that may act as ballast, helping to anchor the beastie in its home waters of a Mexican lake. The discovery, described in the April 27Science, is the first report of such a microbe creating calcified structures inside its cells, rather than externally.
Scientists aren't sure what to make of the discovery. Related cyanobacteria play a major role in the planet's geochemical cycles. “It's interesting and opens up possibilities we hadn't thought about before,” says Robert Riding of the University of Tennessee in Knoxville, who wrote a comment on the research in the same issue of Science. Because the microbe is the first of its kind, and so far, has been found in only one place, “it's difficult to know where it will lead,” Riding says.
Geobiologist Karim Benzerara and his colleagues were investigating Lake Alchichica's stromatolites, knobby pillars of sediment and microbes that can form in shallow waters. The researchers cultivated slimy films of the microbes in a lab aquarium. Looking at the slime under a microscope, the team saw that some cells looked like they were filled with little pearl-like granules. “That's when we figured out that there was something special,” says Benzerara of the CNRS Institute of Mineralogy and Physics of Condensed Matter in Paris.
The granules are an unusual mixture of calcium, strontium, barium, magnesium and carbonate. Because the ratios of these ingredients aren't the same in the granules as in the surrounding water, the researchers suspect that the cyanobacteria have some control over formation of the lumps and are actively transporting some of the ingredients into their cells. While the lumps occupy only about 6 percent of a cell, they change the microbe's density, increasing it by 12 percent. This might help the microbes move from the water column to the surface of an underwater rock or stromatolite, the researchers speculate.
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