Virulent bacterium's DNA is sequenced.

Bacteriologists have one more complete genome sequence in their grasp. This time, the deciphered DNA belongs to Staphylococcus aureus, one of the slipperiest infectious organisms to race through a hospital ward.

Besides its nasty habit of releasing toxins in its victims, the bacterium is "resistant to all antibiotics ever developed by humans," says Keiichi Hiramatsu of Juntendo University in Tokyo, who reported the work with his colleagues in the April 21 LANCET.

Many of S. aureus' genes seem to have come from other organisms, including people. The researchers also found that several of its antibiotic-resistance genes sit on pieces of independent, mobile DNA called plasmids and transposons. The genes that give the bacterium its virulence have multiplied numerous times in the genome, the scientists report.

At any given time, one-third of people carry S. aureus harmlessly, but "given the opportunity, it causes a whole range of diseases from simple abscess to fatal blood poisoning," says Dlawer Ala'Aldeen of Nottingham University in England. The work will help scientists rethink strategies for combating infections and antibiotic resistance, says Ala'Aldeen.