Searching the web, I've come across some interesting information regarding the nature of the anthrax traced to Dr. Ivins.
First of all, it may be important to note that Ivins co-authored a research paper outlining the use of aerosolized anthrax on rhesus monkeys, so in fact he was using live anthrax spores in aerosolized form on live subjects to test effectiveness of anthrax vaccines:
http://www.anthrax.osd.mil/documents/library/efficacyExperimental.pdf
...
B.anthracis challenge
Spores of the virulent B. anthracis Ames strain
were harvested from shaking broth ... After minute respiratory volumes
were measured, animals were exposed in a head-only chamber to a spore
aerosol generated by a three-jet Collison nebulizer.
Note, this alone does NOT prove that Dr. Ivins handled powdered anthrax in his facility as part of his testing, but could he have been testing weaponized anthrax on the rhesus monkeys?
The following blog questions whether the material in the flask was already treated with advanced materials (weaponized):
http://achievingourcountry.blogspot.com/2008/08/first-search-warrant-in-ivins-case.html
Several crucial pieces of information are missing here. First, we don't have the amount of material that is in RMR-1029 or its status in terms of processing with regard to purity or possible processing to weaponize it. In later sections of the warrant, Ivins is said to also refer to this flask interchangeably as "Dugway Ames Spores -- 1997", so it is entirely possible that the spores in RMR-1029 are treated with advanced materials.
...
So we do know that the material in RMR-1029 is highly purified. We still don't know if it is treated in any way to make it more dangerous. We also know that the flask is "large" but still have no idea how much material is there.
This New Scientist article from 2002 notes:
http://www.newscientist.com/article/dn2265-anthrax-attack-bug-identical-to-army-strain.html
So strain D seems to have come from Dugway. The difference between D and the attack strain is not great - there are 36 adenines in a row, instead of 35 - but Keim's team made doubly sure by sequencing that part of the D strain's genome.
This New Scientist article dated Aug. 7, 2008 notes that Ivins was the sole custodian of spores produced by the Army at Dugway:
http://www.newscientist.com/channel/being-human/dn14486-investigators-confident-ivins-was-anthrax-attacker.html?feedId=online-news_rss20
Crucially, they say Ivins was "sole custodian" of a single batch of spores of the Ames strain of anthrax, produced at the army's Dugway facility in Utah in 1997 and stored in a containment lab at USAMRIID.
Then there is this odd claim!
The documents say little about the most difficult step in the process – producing a fine, dry spore powder. They say Ivins simply grew fresh bacteria from the batch for each round of mailings, then dried them.
Their only basis for this claim is that two envelopes addressed to the media also contained a common soil bacterium, which they say got in during culture.
There are other ways such a contaminant could get in, however. The Dugway material should already have been powdered, and the attacker could simply have packaged it, which would have required little skill.
Finally, as I have noted in previous posts, there is this Baltimore Sun article from 2001 where it is noted:
http://www.ph.ucla.edu/epi/bioter/anthraxmatchesarmyspores.html
Most anthrax testing at Dugway, in a barren Utah desert 87 miles southwest of Salt Lake City, is done using the killed spores to reduce the chance of accidental exposure of workers there. But some experiments require live anthrax, milled to the tiny particle size expected on a battlefield, to test both decontamination techniques and biological agent detection systems, the sources say.
...
Anthrax is also grown at the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick, where it is used chiefly to test the effectiveness of vaccines in animals. But that medical program uses a wet aerosol fog <see research article above> of anthrax rather than the dry powder used in the attacks and at Dugway, according to interviews and medical journal articles based on the research.
...
Scientists familiar with the anthrax program at Dugway described it to The Sun on the condition that they not be named. The offensive program made hundreds of kilograms of anthrax for bombs designed to kill enemy troops over hundreds of square miles. Dugway's Life Sciences Division makes the deadly spores in far, far smaller quantities, rarely accumulating more than 10 grams at a time, according to one Army official.
Scientists estimate that the letter sent to Senate Majority Leader Tom Daschle originally contained about 2 grams of anthrax, about one-sixteenth of an ounce, or the weight of a dime. But its extraordinary concentration - in the range of 1 trillion spores per gram - meant that the letter could have contained 200 million times the average dose necessary to kill a person. Dugway's weapons-grade anthrax has been milled to achieve a similar concentration, according to one person familiar with the program.