Microbe with stripped-down DNA may hint at secrets of life

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New York (AP) – Scientists have deleted nearly half the genes of a microbe, creating a stripped-down version that still functions, an achievement that might reveal secrets of how life works.

It may also help researchers create new bacteria tailored for making medicines and other valuable substances.

The newly created bacterium has a smaller genetic code than does any natural free-living counterpart, with 531,000 DNA building blocks containing 473 genes. (Humans have more than 3 billion building blocks and more than 20,000 genes).

But even this stripped-down organism is full of mystery.  Scientists say they have little to no idea what a third of its genes actually do.

“We’re showing how complex life is, even in the simplest of organisms,” researcher J. Craig Venter told reporters.  “These findings are very humbling.”

Some of the mystery genes may be clues to discovering unknown fundamental processes of life, his colleague Clyde Hutchison III said in an interview.

The DNA code, or genome, is contained in a brand-new bacterium dubbed JCVI-syn3.0.  The genome is not some one-and-only minimal set of genes needed for life itself. For one thing, if the researchers had pared DNA from a different bacterium they would probably have ended up with a different set of genes.  For another, the minimum genome an organism needs depends on the environment in which it lives.

And the new genome includes genes that are not absolutely essential to life, because they help the bacterial populations grow fast enough to be practical for lab work.

The genome is “as small as we can get it and still have an organism that is … useful,” Hutchison said.

One goal of such work is to understand what each gene in a living cell does, which would lead to a deep understanding of how cells work, he said.  With the new bacterium, “we’re closer to that than we are for any other cell,” he said.

Another goal is to use such minimal-DNA microbes as a chassis for adding genes to make the organisms produce medicines, fuels and other substances for uses like nutrition and agriculture, said study co-author Daniel Gibson of Synthetic Genomics.