In a technical tour de force with potentially profound implications for the study of emerging diseases, researchers have built the largest-ever self-replicating organism from scratch.

The organism is a virus based on genome sequences taken from a bat-borne version of SARS, a lethal respiratory disease that jumped from animals to humans in 2002. The synthetic virus could help explain how SARS evolved, and the same approach could be used to investigate other species-hopping killers.

"This gives us a system to more quickly answer the questions of where a virus came from, of how to develop vaccines and treatments for a brand-new virus that leaps to humans like SARS did," said Vanderbilt University microbiologist Mark Denison.