IOt’s so simple that it has only 517 genes- the smallest number known in a free- living life form. Humans, by comparison, have 5,000 times more. As small as it is, this single-celled bacterium stirred up some controversy recently.

It started when Clyde Hutchison, professor of microbiology and immunology, came closer to understanding Mycoplasma genitalium, often found in the human genital tract. Hutchison led a team that found that Mycoplasma needs somewhere between 265 and 350 of its genes to survive and reproduce. You could say they figured out what’s essential for life, as far as Mycoplasma is concerned.

Those words-essential for life-set off some alarms. When Hutchison’s team published their work in the December 10 issue of the journal Science, an editorial ran alongside it. Written by a panel of ethicists convened at the suggestion of one of Hutchison’s coauthors, the editorial raised big questions about this little cell: Does defining a minimal genome define life? If scientists can learn enough about a simple cell to make one of their own, does that mean that life is nothing more than DNA?

The ethicists stated they were concerned about the temptation to “demonize” this research and the danger that the press or public would take it to mean that all life can be reduced to DNA. But they concluded that there was nothing in the research that is morally prohibited. The article and editorial, though, caught the attention of media such as CNN and The New York Times.

Hutchison takes it all in stride. He explains that though scientists have been able to make single genes from scratch for some time, “putting together synthetic genes to make a whole genome is something that no one has tried to do yet. Doing the synthesis would be an expensive and technically difficult thing for the current technology.”

And that’s not why Hutchison studies Mycoplasma anyway. “I’d like to understand how this cell works,” he says. “The idea of understanding how something works is probably more helpful than making some specific product.”

Hutchison has been studying this bacterium off and on for several years. “It’s the simplest cell we know about. If we can understand any cell in all its detail, it should be something like Mycoplasma,” he says. Though Hutchison and his colleagues have narrowed down the possibilities for Mycoplasma’s essential genes, further work needs to be done to pinpoint the exact ones. And scientists still don’t know the purpose of all of Mycoplasma’s genes.

Hutchison is content to continue exploring Mycoplasma and leave the philosophical debates to others. “If you’re trying to talk about ‘what is life’ at the level of how the cell works, the reductionist explanation is satisfying to me,” he says. “I don’t think I’m in a position to make a reductionist sort of explanation that’s satisfying about ‘what is the human condition.’ But ‘how does a bacterium work’. We can answer that.”

Other authors of the Science article are Scott Peterson (Hutchison’s former graduate student), Steve Gill, Robin Cline, Owen White, Claire Fraser, and Hamilton Smith, all of The Institute for Genomic Research (TIGR) in Rockville, Maryland, and J. Craig Venter, founder of TIGR and now head of Celera Genomics.