Genomes inside genomes

Scientists at the University of Rochester and the J. Craig Venter Institute have discovered a copy of the entire genome of Wolbachia, a bacterial parasite, residing inside the genome of its completely different host species Drosophila Ananassae, the fruitfly. To isolate the fly’s genome from the parasite’s, the flies were fed with a simple antibiotic, killing the Wolbachia, but Wolbachia genes were still there. The scientists found that the genes were residing directly inside the second chromosome of the insect, and that some of these genes are even transcribed in uninfected flies, so that copies of the gene sequence are made in cells that could be used to make Wolbachia proteins.