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THE entire genome of the microbe that causes cholera has been sequenced. The
bacterium Vibrio cholerae lives in water and often strikes down people
in the aftermath of wars and disasters, such as the recent floods in Mozambique,
when drinking water becomes tainted. But its sequence suggests that it
didn鈥檛 always have a taste for humans. It appears that an ancient, non-virulent
ancestor acquired an extra chromosome, and many of the genes that allow cholera
to attack people are found on this (Nature, vol 406, p 477). Experts
say the finding should speed development of vaccines and drugs to fight the
disease.