What do the following have in common: the promise of Botox as the key to everlasting youthful looks; E. coli O157 hamburger disease; a mysterious illness which killed 35 heroin users in 2000; and the assassination by poisoned umbrella-tip of a Bulgarian dissident in the 1970s? The answer is that all of these are caused by toxins, the powerful biological poisons released by bacteria and some plant...