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Synthetic bacterium lives with less than 500 genes

Synthetic microbe

Researchers led by genome sequencing pioneer Craig Venter report engineering a microbe to have the smallest genome—and the fewest genes—of any freely living organism. Known as Syn 3.0, the new organism has a genome whittled down to the bare essentials needed to survive and reproduce, just 473 genes. In their current work, Venter, along with project leader Clyde Hutchison at JCVI, set out to determine the minimal set of genes needed for life by stripping nonessential genes. The team systematically whittled away genes that either had nonessential functions or duplicated the function of another gene. In the end, Venter says, his team built, designed, and tested “multiple hundreds” of constructs before settling on Syn 3.0.
The microbe’s genetic structure excites evolutionary biologists and biotechnologists, who anticipate adding genes back to it one by one to study their effects. “It’s an important step to creating a living cell where the genome is fully 
defined,” says synthetic biologist Chris Voigt of the Massachusetts Institute of Technology in Cambridge. But Voigt and others note that this complete definition remains a ways off, because the function of 149 of Syn 3.0’s genes—roughly one-third—
remains unknown. Investigators’ first task is to probe the roles of those genes, which promise new insights into the basic biology of life.
With a total of 531,000 bases, the new organism’s genome isn’t much smaller than that of Mycoplasma genitalium, with 600,000 bases. But M. genitalium grows so slowly that a population of cells can take weeks to double. Syn 3.0, by contrast, has a doubling time of 3 hours, suggesting that it thrives with its slimmed down genome. “We’re not saying this is the ultimate minimum genome; our current knowledge of biology is not sufficient to sit down and design a living organism and build it”, says Venter.