Daan Goosen's calling card to the FBI was a vial of bacteria he had freeze-dried and hidden inside a toothpaste tube for secret passage to the US. From among hundreds of flasks in his Pretoria lab, the South African scientist picked a man-made strain that was sure to impress: a microbial Frankenstein that fused the genes of a common intestinal bug with DNA from the pathogen that causes the deadly illness gas gangrene. "This will show the Americans what we are capable of," Mr Goosen said then. On May 6 last year, Mr Goosen slipped the parcel to a retired...