News of the WeekAnthrax Investigation

Silicon Mystery Endures in Solved Anthrax Case

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Science  19 Mar 2010:
Vol. 327, Issue 5972, pp. 1435
DOI: 10.1126/science.327.5972.1435

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Summary

Scientists inside and outside the government say there is clear evidence that the high levels of silicon found in the anthrax used in the 2001 letter attacks came not from anything added to "weaponize" the anthrax spores—as researchers had suggested early in the probe—but from the culture in which the spores were grown. That evidence may have settled the issue of whether the anthrax was weaponized, at least for scientists familiar with the case. But it raises a different question: Why did the mailed anthrax have such a high proportion of spores with a silicon signature in comparison to most other anthrax samples?