Anthrax update: germ-on-germ warfare

Science World, Oct 18, 2002 by Kim Y. Masibay

Until a year ago, most people thought of anthrax as the bacteria that lurked in soil and occasionally infected an unlucky farm animal that inhaled the microbes. But shortly after the terrorist attacks of September 11, anthrax panic swept the nation: Someone weaponized the single-celled bacterium by processing its hardy reproductive particles, or spores, into fine dry powder. The culprit laced a series of letters with these spores and mailed them--killing five recipients and infecting 18 others who unwittingly inhaled or touched the microbes. "We now know that anthrax is a real threat," says microbiologist (scientist who studies tiny life forms) Vincent Fischetti at Rockefeller University in New York City.

Weaponized spores are so small, "10,000 of them are like a speck of dust," says bio-warfare expert Jonathan Tucker at the Monterey Institute of International Studies in Washington, D.C. It takes 10,000 spores to trigger a full-blown case of inhalation anthrax, which begins like a flu and ends in death.

"Once inhaled, the spores germinate like seeds and multiply," Tucker says. Bacterial toxins (poisons) flood the bloodstream to overwhelm the immune system and cause septic shock: blood vessels leak, blood pressure drops, and organs fail.

A year has passed and the anthrax mailer is still at large. But last August, a research team led by Fischetti discovered a versatile anthrax-killing agent that could be used as medicine, as a surface decontaminant, and as a spore detector. The agent: a bacteria-eating enzyme (a protein, or compound, that speeds up a chemical reaction), "This enzyme is almost as effective as pouring bleach over the organisms," says team microbiologist Raymond Schuch. A few drops of the enzyme, called lysin, can promptly destroy a test tube worth of anthrax.

Ironically, the enzyme is made by a virus: a smaller, simpler microbe than a bacterium. This particular type of Virus--known as a bacteriophage or simply "phage"--evolved to invade only anthrax bacteria. In nature, there's a phage for every type of bacteria. Once a phage infects a bacterial cell, it replicates by the hundreds inside it, then emits lysine, which chews through the bacterium's cell membrane, or outer skin. The cell dies instantly. "It's an entirely new way of controlling bacteria," Fischetti says.