Others are pursuing a far more radical approach. Soon after the State of the Union speech, Patrinos left the DOE to become president of Synthetic Genomics, a startup in Rockville, MD, founded by Craig Venter, the iconoclastic biologist who led the private effort to decode the human genome. Synthetic Genomics is in hot pursuit of a bacterium “that will do everything,” as Venter puts it. With funding from Synthetic Genomics, scientists at the J. Craig Venter Institute are adding and subtracting genes from natural organisms using the recombinant techniques employed by other microbial engineers. In the long run, however, Venter is counting on an approach more in keeping with his reputation as a trailblazer. Rather than modify existing organisms to produce ethanol and other potential biofuels, he wants to build new ones.
Natural selection, argues Venter, does not design life forms to efficiently perform the multitudinous functions their genes encode, much less to carry out a dedicated task like ethanol production. Consequently, a huge amount of effort and expense goes toward figuring out how to shut down complex, often redundant genetic pathways that billions of years of evolution have etched into organisms. Why not start with a genome that has only the minimal number of genes needed to sustain life and add to it what you need? “With a synthetic cell, you only have the pathways in there that you want to be in there,” he says.
Synthetic Genomics’ approach is based on research that Venter’s Institute for Genomic Research conducted on a microörganism called Mycoplasma genitalium in the late 1990s. The microbe, which dwells in the human urinary tract, has only 517 genes. While that’s the smallest genome seen in any life form known, researchers in Venter’s group showed that the organism could survive even after they had knocked out almost half of its protein-coding genes (some genes code not for proteins but for other biomolecules that perform regulatory functions within the cell). Using the DNA sequence of this “minimal genome” as a guide, they are now attempting to synthesize an artificial chromosome that, inserted into a hollowed-out cell, will lead to a viable life form. Once they are over this first hurdle, they plan to build synthesized, task-specific genetic pathways into the genome, much the way one might load software onto a computer’s operating system. Rather than create spreadsheets or do word processing, however, such “biologically based software” would instruct the cell to break down cellulose to produce ethanol or carry out other useful functions. “This is a totally new field on the verge of explosion,” says Venter.
Among biofuels, ethanol is the established front-runner, but various types of microbes also produce hydrogen, methane, biodiesel, and even electricity – which means they could be genetically engineered to produce more of these resources. At the University of California, Berkeley, bioengineer Jay Keasling and his colleagues are proposing to design organisms that pump out a fuel no natural microbe makes, one that offers some alluring advantages over ethanol: gasoline. Its virtues as a fuel are proven, of course, and the ability to produce it from waste wood and waste paper, which Keasling thinks is feasible, could reduce countries’ dependence on foreign oil. And unlike ethanol, which is water soluble and must be transported in trucks lest it pick up water in pipes, biologically generated octane could be economically piped to consumers, just like today’s gas.
“Ethanol has a place, but it’s probably not the best fuel in the long term,” says Keasling. “People have been using it for a long time to make wine and beer. But there’s no reason we have to settle for a 5,000-year-old fuel.”
In the short term, some advances in biology and engineering are needed before fuels made from biomass will be practical and competitive with fossil fuels. But in the longer term, says Venter, “we’re limited mostly by our imagination, not by the limits of biology.”
Jamie Shreeve’s most recent book is The Genome War.