Geo-microbiologists from Arizona State University have solved a long-standing conundrum about how some photosynthetic microorganisms, endolithic cyanobacteria, bore their way into limestone, sand grains, mussel shells, coral skeletons and other substrates composed of carbonate.
According to the lead investigator, ASU professor Ferran Garcia-Pichel, the answer to the mystery of what is "at the heart of an erosive force of global proportions" is a calcium-driven pump, similar to that which we use to power our muscles.
The results of Garcia-Pichel's study "Microbial excavation of solid carbonates powered by P-type ATPase-mediate transcellular Ca 2+ transport" were published Nov. 29 in the Proceedings of the National Academy of Sciences (PNAS).
While the dissolution of the carbonate coral reefs was noted more than a century ago by Louis Agassiz, the father of American naturalists, the specifics of how this physiological process occurs has remained a mystery. In fact, the process has presented a geochemical paradox to scientists, in that most cyanobacteria tend to precipitate new carbonates, not dissolve them.
Typically cyanobacteria, by photosynthesizing, raise the pH of the water (and lower the acidity); this process typically causes carbonate to precipitate if the change is large enough. While that is the "normal" case, the paradox with boring cyanobacteria is that photosynthesis occurs at the same time that they dissolve carbonate structures (which typically requires the pH to go down, making the environment more, rather than less acidic).
Garcia-Pichel and coauthors, Edgardo Ramrez-Reinat, a doctoral candidate, and Qunjie Gao, a faculty research associate, in the School of Life Sciences in ASU's College of Liberal Arts and Sciences, set about trying to understand how this select group of carbonate-boring species can excavate by coaxing a strain of Mastigocoleus testarum, a filamentous, branching cya
|Contact: Margaret Coulombe|
Arizona State University