Scientists Unravel Anthrax Bacterium

Scientists have published the genetic structure of the Ames strain of anthrax, the bacterium that killed five people in the 2001 mail attacks.

The work reveals a microbe well-adapted for a meat-eating lifestyle, as befits a bacterium that infects a wide range of mammals from zebras on the Serengeti to cattle on the Texas range. The analysis of Bacillus anthracis’ genetic sequence, published Thursday in the journal Nature, also provided clues to the noxious bacterium’s ancestry. Lurking in its DNA are instructions for digesting insect molecules, suggesting that anthrax was descended from a microbe that preyed on dead or living bodies of insects.

The decoding of the B. anthracis genome was led by researchers at the Institute for Genomic Research, in Rockville, Md. They and another research team then compared the anthrax genome with several near relatives, principally Bacillus cereus, a microbe that normally resides peacefully in the soil but can cause food poisoning.

The genomes were remarkably similar: There were only about 150 significant changes among the roughly 5,000 genes. Like B. cereus, anthrax has many features of a soil-growing bug. But it “is a soil-growing bug gone bad,” said Tim Read, lead researcher of the sequencing work. The anthrax genome has acquired extra genes for invading and growing in animals.

The microbe also has fewer genes than B. cereus for the digestion of plant carbohydrates, but has extra ones involved in the transport and chopping up of bits of protein and amino acids found in meat.