Taking a small step toward synthetic biological systems, scientists have replaced the entire genome of a bacterial cell with one from a closely related species (Science, DOI: 10.1126/science.1144622). This so-called genome transplant could someday allow researchers to create microorganisms with synthetic genomes specifically engineered to produce biofuels or to sequester carbon from the environment, for example. To prove that such a transplant is possible, John I. Glass and colleagues at the J. Craig Venter Institute, Rockville, Md., took the genome—in the form of naked DNA, virtually free of protein—from the bacterium Mycoplasma mycoides and transplanted it into the closely related bacterium Mycoplasma capricolum. By comparing genetic and other biological traits, they confirmed a clean change of one bacterial species into another with no recombination between the incoming or outgoing chromosomes. The researchers have filed for a patent on the transplanting technique.