Taking a significant step toward the creation of synthetic forms of life, researchers reported Thursday that they had manufactured the entire genome of a bacterium by stitching together its chemical components.

Scientists had previously constructed the complete DNA of viruses, but this is the first time it has been done for bacteria, which are far more complex. The genome is more than 10 times as long as the longest piece of DNA ever synthesized.

The feat is a watershed for the emerging field called synthetic biology, which involves the design of organisms to perform particular tasks, like making biofuels. Synthetic biologists envision being able to design an organism on a computer, press the “print” button to have the necessary DNA made and then put that DNA into a cell to produce a custom-made creature.

“What we are doing with the synthetic chromosome is going to be the design process of the future,” said J. Craig Venter, the boundary-pushing gene scientist.

Dr. Venter assembled the team that made the bacterial genome as part of his well-publicized quest to create the first synthetic organism. The work was published online Thursday by the journal Science.