"The researchers constructed a bacterium's "genetic software" and transplanted it into a host cell.
The resulting microbe then looked and behaved like the species "dictated" by the synthetic DNA.
The advance, published in Science, has been hailed as a scientific landmark, but critics say there are dangers posed by synthetic organisms.
The researchers hope eventually to design bacterial cells that will produce medicines and fuels and even absorb greenhouse gases.
Craig Venter defends the synthetic living cell
The team was led by Dr Craig Venter of the J Craig Venter Institute (JCVI) in Maryland and California."