Fruit fly parasite's gene invasion raises questions over evolution

Scientists have found the genes of an organism fused wholesale into the genome of an entirely separate species, raising new questions over how evolution works. The discovery suggests that simple bacteria and animals might swap entire genes more often than previously thought. Such large-scale transfer of genes would allow species to acquire entirely new functions and abilities in a very short space of time, rather than the much slower sequence of random mutations that normally evolves species over several generations.

Jack Werren, a biologist at the University of Rochester, led a team to studying fruit flies infected with Wolbachia, a parasitic bacterium which invades 70% of the world's invertebrates and has developed a symbiotic relationship with many, co-evolving with them. Once Wolbachia invades a member of a species, it eventually makes its way into the host's eggs or sperm, ensuring it is passed on to the next generation of fruit flies. "The parasite's entire or nearly entire genome has been absorbed and integrated into the host's. The host's genes actually hold the coding information for a completely separate species," said Prof Werren.

Jonathan Sherwood, of the University of Rochester, said the discovery might have implications for gene-sequencing projects around the world, which normally discard bacterial genes from their samples, tagging them as contaminants. It might also shed light on human evolution.