Anthrax gene code unravelled

The complete genetic sequence of the feared bacterium which causes anthrax has been de-coded by scientists.

Researchers are seeking to develop new drugs or vaccines against anthrax

The breakthrough could help doctors come up with better ways to protect people in the event of a bioterror attack.

A team from The Institute for Genomic Research (Tigr) spent four years unravelling the genome of the virulent Ames strain of Bacillus anthracis, and their results are described in the journal Nature.

The Ames strain is the variety most commonly associated with anthrax biological weapons, and was used in the mail attacks in the US in late 2001 which killed five people.

Some studies predict a kilogram of anthrax spores dropped on a city of 10 million people would result in more than 100,000 deaths - even if every infected person was given antibiotics.

Researchers have also completed the sequencing of a soil bug called Bacillus cereus - and found it appears to be closely related to the anthrax bacterium.

Scientists are trying to find out why the anthrax bug produces far more powerful toxins compared with Bacillus cereus, even though the two share so many genetic traits.

This could lead to possible strategies to help infected patients.

Inhaled disease

The president of Tigr, Dr Claire Fraser, said: "The genome sequence will benefit research projects to find targets for new drugs and vaccines as well as to improve anthrax detection and diagnosis."

BACILLUS ANTHRACIS GENOME

The "life code" of the anthrax bacterium is written in its DNA, the double-stranded molecule held together by chemical components called bases

Adenine (A) bonds with thymine (T) and cytosine(C) bonds with guanine (G) to spell out the instructions that build and maintain the cell

The bacterium has more than five million of these letters, wound into one large bundle, or chromosome, and two smaller ringed structures called plasmids

Written in the DNA are almost 6,000 genes which the cell uses as templates to make proteins; these sophisticated molecules control all its functions

It is the plasmids that carry genes related to virulence and toxicity that account for much of the lethal power of anthrax to kill animals, including humans

Other strains of anthrax with different characteristics are also being sequenced to assist researchers as they try to work out the key genes which make the bug so deadly.

Natural cases of anthrax are uncommon, but do happen every year.

Most of these happen after anthrax spores have come into contact with the skin, producing a less severe form of the disease.

The most deadly infections arise when people inhale, or ingest, spores.

In these cases, unless antibiotics are given swiftly, the fatality rate is high.

UK scientists are enthusiastic about the success of the project.

Dr Colin Berry, from the Cardiff School of Biosciences, told BBC News Online: "It's likely to be very significant - having the whole genome gives us the complete picture.

"There will be no immediate response or cure, but it provides the potential for new cures in the future.

"Even if we had only 99% of the sequence of the bacterium, we would always be wondering if there was something we had missed.

"Scientists have the technology now which allows them to see exactly which genes are switched on or off. Having this information may reveal chinks in the armour of anthrax."

The bacterium is also lethal to wild animals and livestock

Another bacterial specialist, Dr Chris Wilmott, from the University of Leicester, warned that the genome data would not bear fruit for patients for some time - and doctors would have to be careful not to over-use effective drugs in the meantime.

He told BBC News Online: "Bacterial species have increasingly become resistant to existing antibiotics, so the identification of potential new targets is very important in enabling us to fight back.

"Having said that, we also need to remember that knowing about a new target is not the same as having a new drug to fight infection right here, right now."