Genetic Gumshoeing in the Anthrax Letter Attacks

The techniques used to trace the Bacillus anthracis spores from the 2001 "anthrax" letter attacks to the USAMRIID laboratory at Fort Detrick, Maryland, weren't particularly novel, according to a report in this week's Science. By using documents released by the DoJ last week and expert speculation, writer Martin Enserink proposes the series of events that led to the source of the B. anthracis (Ames strain) that killed 5 people.

The first major task was to genetically distinguish the letter spores on the basis of phenotypic differences in cultured bacterial subpopulations, if at all possible.

The FBI likely identified the USAMRIID lab as the source of the letter spores given that it was the only lab within the area where the "federal eagle" envelopes used in the attacks were distributed and sold. Although this very sound conclusion does not completely rule out the possibility that the spores came from another lab, it is the confluence of evidence (including Ivins's alleged submission of sabotaged or false B. anthracis samples to the FBI) that indicts the former USAMRIID scientist.

SNPs = single nucleotide polymorphisms.

* Sequencing work was likely performed by scientists at Northern Arizona University and The Institute for Genomic Research (TIGR) in Rockville, Maryland.

08/18/08 update: According to ABC News, 8 of the positive samples originated from 2 US labs. One is presumed to be USAMRIID, and the other is not named. The original (2002), "unusable" sample of B. anthracis provided by Bruce Ivins to the FBI—a portion of which was retained by Paul Keim at Northern Arizona University—later tested positive for the 4 "letter" mutations.