A Boring Life

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Science  07 Jan 2011:
Vol. 331, Issue 6013, pp. 11
DOI: 10.1126/science.331.6013.11-b

In the deep oceans, carbonate minerals precipitate slowly, forming the building blocks of limestone or the shells of many marine organisms. Some filamentous bacteria, including photosynthetic autotrophs, can bore deep into these carbonates, but this biological mining process remains a paradox; photosynthesis usually causes carbonates to grow, not dissolve. Garcia-Pichel et al. showed how one type of cyanobacteria—originally isolated from a marine snail shell—was able to bore into chips of calcite (CaCO3) in laboratory experiments by controlling the saturation state of calcium. A number of tests, including enzyme-inhibition assays and fluorescence microscopy, suggest that these bacteria used a calcium-ion pump to transport calcium from the boring front, through the cell, and then back out toward the top of the bore hole. Furthermore, based on experiments in both light and dark conditions, boring was probably not directly related to photosynthetic activity. If this mechanism is widespread in other marine carbonates, inhibiting calcium-ion pumps in some cyanobacteria could slow the destructive dissolution of coral reefs and shellfish.

Proc. Natl. Acad. Sci. U.S.A. 107, 21749 (2010).

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