or mutations in the anthrax cultures grown from powder found in the letters. scientists at tigr sequenced the complete genomes from many of these isolates during the period from 2002 to 2004. this sequencing identified three relatively large changes in some of the isolates, each comprising a region of dna that had been duplicated or triplicated. the size of these regions ranged from 823 to 2607 base pairs, and all occurred near the same genes. details of these mutations were published in 2011 in the proceedings of the national academy of sciences. these changes became the basis of pcr assays used to test other samples to find any that contained the same mutations. the assays were validated over the many years of the investigation, and a repository of ames samples was also built. from roughly 2003 to 2006 the repository and the screening of the 1,070 ames samples in that repository were completed. based on the testing, the fbi concluded that flask rmr-1029 was the parent material of the anthrax spore powder. ivins had sole control over that flask.: 28–29 controversy over coatings and additives on october 24, 2001, usamriid scientist peter jahrling was summoned to the white house after he reported signs that silicon had been added to the anthrax recovered from the letter addressed to daschle. silicon would make the anthrax more capable of penetrating the lungs. seven years later, jahrling told the los angeles times on september 17, 2008, "i believe i made an honest mistake", adding that he had been "overly impressed" by what he thought he saw under the microscope. richard preston's book the demon in the freezer provides details of conversations and events at usamriid during the period from october 16, 2001, to october 25, 2001. key scientists described to preston what they were thinking during that period. when the daschle spores first arrived at usamriid, the key concern was that smallpox viruses might be mixed with the spores. "jahrling met ezzell in a hallway and said, in a loud voice, 'goddamn it, john, we need to know if the powder is laced with smallpox.'" thus, the initial search was for signs of smallpox viruses. on october 16, usamriid scientists began by examining spores that had been "in a milky white liquid" from "a field test done by the fbi's hazardous materials response unit". liquid chemicals were then used to deactivate the spores. when scientists turned up the power on the electron beam of the transmission electron microscope (tem), "the spores began to ooze." according to preston, "whoa," jahrling muttered, hunched over the eyepieces. something was boiling off the spores. "this is clearly bad stuff," he said. this was not your mother's anthrax. the spores had something in them, an additive, perhaps. could this material have come from a national bioweapons program? from iraq? did al-qaeda have anthrax capability that was this good? on october 25, 2001, the day after senior officials at the white house were informed that "additives" had been found in the anthrax, usamriid scientist tom geisbert took a different, irradiated sample of the daschle anthrax to the armed forces institute of pathology (afip) to "find out if the powder contained any metals or elements". afip's energy-dispersive x-ray spectrometer reportedly indicated "that there were two extra elements in the spores: silicon and oxygen. silicon dioxide is glass. the anthrax terrorist or terrorists had put powdered glass, or silica, into the anthrax. the silica was powdered so finely that under geisbert's electron microscope it had looked like fried-egg gunk dripping off the spores." the "goop" peter jahrling had seen oozing from the spores was not seen when afip examined different spores killed with radiation. the controversy began the day after the white house meeting. the new york times reported, "contradicting some u.s. officials, 3 scientists call anthrax powder high-grade – two experts say the anthrax was altered to produce a more deadly weapon", and the washington post reported, "additive made spores deadlier". countless news stories discussed the "additives" for the next eight years, continuing into 2010. later, the fbi claimed a "lone individual" could have created the anthrax spores for as little as $2,500, using readily available laboratory equipment. a number of press reports appeared suggesting the senate anthrax had coatings and additives. newsweek reported the anthrax sent to senator leahy had been coated with a chemical compound previously unknown to bioweapons experts. on october 28, 2002, the washington post reported "fbi's theory on anthrax is doubted", suggesting that the senate spores were coated with fumed silica. two bioweapons experts that were utilized as consultants by the fbi, kenneth alibek and matthew meselson, were shown electron micrographs of the anthrax from the daschle letter. in a november 5, 2002 letter to the editors of the washington post, they stated that they saw no evidence the anthrax spores had been coated with fumed silica. in science magazine, one group of scientists said that the material could have been made by someone knowledgeable with standard laboratory equipment. another group said it "was a diabolical advance in biological weapons technology". the article describes "a technique used to anchor silica nanoparticles to the surface of spores" using "polymerized glass". an august 2006 article in applied and environmental microbiology, written by douglas beecher of the fbi labs in quantico, virginia, states "individuals familiar with the compositions of the powders in the letters have indicated that they were comprised simply of spores purified to different extents." the article also specifically criticizes "a widely circulated misconception" "that the spores were produced using additives and sophisticated engineering supposedly akin to military weapon production". the harm done by this misconception is described this way: "this idea is usually the basis for implying that the powders were inordinately dangerous compared to spores alone. the persistent credence given to this impression fosters erroneous preconceptions, which may misguide research and preparedness efforts and generally detract from the magnitude of hazards posed by simple spore preparations." critics of the article complained that it did not provide supporting references. false report of bentonite in late october 2001, abc chief investigative correspondent brian ross linked the anthrax sample to saddam hussein because of its purportedly containing the unusual additive bentonite. on october 26, ross said, "sources tell abcnews the anthrax in the tainted letter sent to senate majority leader tom daschle was laced with bentonite. the potent additive is known to have been used by only one country in producing biochemical weapons—iraq. ... t is a trademark of iraqi leader saddam hussein's biological weapons program ... the discovery of bentonite came in an urgent series of tests conducted at fort detrick, maryland, and elsewhere." on october 28, ross said that "despite continued white house denials, four well-placed and separate sources have told abc news that initial tests on the anthrax by the u.s. army at fort detrick, maryland, have detected trace amounts of the chemical additives bentonite and silica", a charge that was repeated several times on october 28 and 29. on october 29, 2001, white house spokesman scott stanzel "disputed reports that the anthrax sent to the senate contained bentonite, an additive that ha been used in iraqi president saddam hussein's biological weapons program". stanzel said, "based on the test results we have, no bentonite has been found". the same day, major general john parker at a white house briefing stated, "we do know that we found silica in the samples. now, we don't know what that motive would be, or why it would be there, or anything. but there is silica in the samples. and that led us to be absolutely sure that there was no aluminum in the sample, because the combination of a silicate, plus aluminum, is sort of the major ingredients of bentonite." just over a week later, homeland security advisor tom ridge in a white house press conference on november 7, 2001, stated, "the ingredient that we talked about before was silicon." neither ross at abc nor anyone else publicly pursued any further claims about bentonite, despite ross's original claim that "four well-placed and separate sources" had confirmed its detection. dispute over silicon content some of the anthrax spores (65–75%) in the anthrax attack letters contained silicon inside their spore coats. silicon was even reportedly found inside the natural spore coat of a spore that was still inside the "mother germ", which was asserted to confirm that the element was not added after the spores were formed and purified, i.e., the spores were not "weaponized". in 2010, a japanese study reported, "silicon (si) is considered to be a "quasiessential" element for most living organisms. however, silicate uptake in bacteria and its physiological functions have remained obscure." the study showed that spores from some species can contain as much as 6.3% dry weight of silicates. "for more than 20 years, significant levels of silicon had been reported in spores of at least some bacillus species, including those of bacillus cereus, a close relative of b. anthracis." according to spore expert peter setlow, "since silicate accumulation in other organisms can impart structural rigidity, perhaps silicate plays such a role for spores as well." the fbi lab concluded that 1.4% of the powder in the leahy letter was silicon. stuart jacobson, a small-particle chemistry expert stated that: this is a shockingly high proportion . it is a number one would expect from the deliberate weaponization of anthrax, but not from any conceivable accidental contamination. scientists at the lawrence livermore national laboratory conducted experiments in an attempt to determine if the amount of silicon in the growth medium was the controlling factor which caused silicon to accumulate inside a spore's natural coat. the livermore scientists tried 56 different experiments, adding increasingly high amounts of silicon to the media. all of their results were far below the 1.4% level of the attack anthrax, some as low as .001%. the conclusion was that something other than the level of silicon controlled how much silicon was absorbed by the spores. richard o. spertzel, a microbiologist who led the united nations' biological weapons inspections of iraq, wrote that the anthrax used could not have come from the lab where ivins worked. spertzel said he remained skeptical of the bureau's argument despite the new evidence presented on august 18, 2008, in an unusual fbi briefing for reporters. he questioned the fbi's claim that the powder was less than military grade, in part because of the presence of high levels of silica. the fbi had been unable to reproduce the attack spores with the high levels of silica. the fbi attributed the presence of high silica levels to "natural variability". this conclusion of the fbi contradicted its statements at an earlier point in the investigation, when the fbi had stated, based on the silicon content, that the anthrax was "weaponized", a step that made the powder more airy and required special scientific know-how. "if there is that much silicon, it had to have been added," stated jeffrey adamovicz, who supervised ivins' work at fort detrick. adamovicz explained that the silicon in the anthrax attack could have been added via a large fermentor, which battelle and some other facilities use but "we did not use a fermentor to grow anthrax at usamriid ... we did not have the capability to add silicon compounds to anthrax spores." ivins had neither the skills nor the means to attach silicon to anthrax spores. spertzel explained that the fort detrick facility did not handle anthrax in powdered form. "i don't think there's anyone there who would have the foggiest idea how to do it." investigation a reward for information totalling $2.5 million is being offered by the fbi, u.s. postal service and advo, inc. authorities traveled to six continents, interviewed over 9,000 people, conducted 67 searches and issued over 6,000 subpoenas. "hundreds of fbi personnel worked the case at the outset, struggling to discern whether the sept. 11 al-qaeda attacks and the anthrax murders were connected before eventually concluding that they were not." in september 2006, there were still 17 fbi agents and 10 postal inspectors assigned to the case, including fbi special agent c. frank figliuzzi who was the on-scene commander of the evidence recovery efforts. anthrax archive destroyed the fbi and centers for disease control and prevention (cdc) both gave permission for