Anthrax preparation indicates home-grown origin

by Debora MacKenzie

As anthrax continues to turn up in US postal facilities, and postal
workers, evidence is emerging that it is an American product. Not only 
are the bacteria genetically close to the strain the US used in its own
anthrax weapons in the 1960s, but New Scientist can reveal that the 
spores also seem to have been prepared according to the secret US 
"weaponisation" recipe.

This is troubling, say bioterrorism specialists. While the terrorists
behind the anthrax-laced mail US might have got hold of the strain of
anthrax in several laboratories around the world, the method the US
developed for turning a wet bacterial culture into a dangerous, dry 
powder is a closely-guarded secret.

Its apparent use in the current spate of attacks could mean the secret 
is out. An alternative is that someone is using anthrax produced by the 
old US biological weapons programme that ended in 1969 - in which case the
scope for further attacks could be limited. Experiments to determine 
which is true are underway now in the US.

Particle size

Analysis of the physical form of the anthrax powder used in the attacks
has lagged behind the genetic analysis. Bacteria from patients or
contaminated surfaces can be multiplied up to provide enough DNA for
analysis. But a physical examination requires a sample of the actual
powder, and so far, only two are known. One is from the letter opened 
in Senator Tom Daschle's office in Washington on 15 October, the other 
from a letter sent to the New York Post.

Last week, US Senator Bill Frist announced that the powder in the 
Daschle letter was in particles 1.5 to 3.0 microns wide, a very narrow size 
range. The results of the physical analysis of the New York Post letter are 
not yet known.

The actual bacterial spore is ovoid and around half a micron wide. The
whole trick to making anthrax weapons, says Ken Alibek, the former 
deputy head of the Soviet Union's bioweapons programme, is to turn wet 
cultures of bacteria into dry clumps of spores that are each between one and 
five microns wide, the optimal size to penetrate a human lung and stay 

But dried spores tend to form larger particles, with a static electric
charge that makes them cling doggedly to surfaces rather than floating
through the air where they can be inhaled.

Fluidising agent

The Soviet Union got around this by grinding dried cultures along with
chemicals that cause the particles to remain separate. Iraq is the only
other state known to have tried making such a weapon, and it dried 
anthrax cultures along with bentonite, a clay used as a fluidising agent in
powders. But last week the White House said there was no bentonite in 
the Daschle letter.

For its weapon, say informed sources, the US added various molecules,
including surfactants, to the wet spores so that when they were dried,
they broke up into fine particles within a very narrow size range of a 
few microns. There was no need to grind the powder further. Chemical tests 
are now being conducted to see if any traces of the US additives are 

Grinding was considered the most likely way for terrorists to create
anthrax powders, as the milling machinery is not hard to obtain. But it
results in a wider range of particle sizes. Large particles can be
filtered out, but smaller ones remain. The Daschle anthrax, say 
sources, looks instead like it was made according to the US recipe.

Anthrax stockpile

The question is, when? At its peak, the US bioweapons programme made 
900 kilograms of dry anthrax powder per year at a plant in Arkansas. That
stockpile was destroyed when the US renounced bioweapons in 1969. But
small samples might have been saved without being noticed.

Experiments are now underway in the US to determine how many bacterial
generations separate the anthrax being used in the attacks from the 
most closely related strains in a reference collection of anthrax, which
includes the US weapons strain.

If the number is very small, and the anthrax closely resembles the 
weapons strain genetically, it could be a leftover from weapons production 
before 1969.

If, however, the bacteria have gone through many cell divisions since 
the most closely related strain was frozen, they might have been produced 
more recently. That would mean someone has obtained not only a virulent 
strain of anthrax, but the know-how to turn it into what was probably the most
sophisticated anthrax weapon ever produced.


Back To Islam Awareness Homepage

Latest News about Islam and Muslims

Contact for further information