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Last Updated

01 May 2003

Source: New York Times, May 1, 2003

Anthrax Is Found Similar to Common Soil Bacterium


Scientists have decoded the genome of the anthrax bacterium and found that it closely resembles that of a common soil bacterium.

The finding, published today in the journal Nature, is expected to help scientists pinpoint the genetic machinery that makes anthrax so deadly and devise therapies against it.

The type of anthrax that was decoded is known as the Ames strain, a particularly deadly form that has long been studied in biological weapons laboratories and was used in the anthrax mailings.

The genome was decoded by a team at the Institute for Genomic Research in Rockville, Md., led by Dr. Timothy D. Read. The institute started to make the genome sequence available on its Web site when decoding began in 1999, and today published its analysis of the full genome and a comparison with a closely related soil bacterium, Bacillus cereus. The cereus genome was decoded by Dr. Natalia Ivanova and colleagues at Integrated Genomics in Chicago.

The anthrax genome consists of a large, circular chromosome containing 5,227,293 units of DNA. These encode the information for 5,508 genes, Dr. Read's team reports. The bacterium also possesses two much smaller rings of DNA, known as plasmids, one of which carries its three toxin-making genes. Its cereus cousin has a similar main chromosome, but its plasmids lack the toxin genes that make anthrax so deadly.

The genetic repertoire of the anthrax and cereus bacteria includes genes that break down proteins but lacks many genes that metabolize sugars, a common source of energy for other bacteria. This suggests that anthrax and cereus are specialized for consuming animal and plant proteins in the soil, Dr. Read said.

The anthrax bacterium spends most of its time in the soil but has moved up the food chain from scavenger to killer by having acquired its plasmid with the three toxins. Though the plasmid seems to have been acquired recently, in evolutionary terms, it is not yet clear where it came from.

The Ames strain was used in the anthrax mailings sent to the Senate and news media offices in fall 2001. Last year Dr. Read's team analyzed an anthrax sample taken from Robert Stevens (case 5), a photo editor who died after contracting anthrax from a letter sent to the American Media building in Boca Raton, Fla. The aim was to help the Federal Bureau of Investigation determine which of several laboratories known to hold stocks of the Ames strain was the source of the material.

Though a few minor differences were found between the original Ames strain and that used in the letter, it was not clear how helpful that discovery was in identifying the source stock. But Dr. Claire M. Fraser, the president of the Institute for Genomic Research, said the institute was still working on the problem.

"None of the parties involved believe that we are at a dead end," Dr. Fraser said.

Editors of several journals agreed this February to withhold publications that might give help to bioterrorists. Dr. Fraser said that she had held nothing back in publishing the anthrax genome and that no one had asked her to. Dr. Ronald Atlas, president of the American Society of Microbiology and a leading advocate of the restraint policy, said his concern was with cookbook descriptions of how to make biological weapons and he had no wish to curb publication of fundamental knowledge like the sequence of the anthrax genome.