Scientists have created a "minimal cell" with just 473 genes—such work could have huge benefits beyond biologyby Philip Ball / April 4, 2016 / Leave a comment
Read more: There is no intelligence gene… singular
How many genes does it take to make an organism? One answer has just been supplied by researchers at the J. Craig Venter Institute (JCVI) in La Jolla, California, among them biotech entrepreneur Venter himself. They have created a “minimal cell” christened JCVI-syn3.0, based on the bacterium Mycoplasma mycoides but with a tailor-made, synthetic genome stripped of what seem to be all superfluous genes to leave just 473 of them. In the popular but somewhat misleading metaphor, you might say that these cells run on just 473 instructions.
I say “one answer” because there is nothing definitive about this number: it’s just the smallest viable genome so far identified. The question is probably ill-posed, since it depends on what you mean by “life.” Many viruses have much smaller genomes than JCVI-syn3.0, but they are not really autonomous living entities, depending instead on their ability to hijack the genetic machinery of the host organisms they invade.
And when the notion of a minimal cell like this was discussed at the first international meeting on synthetic biology (the engineering of “artificial” organisms) at the Massachusetts Institute of Technology in 2004, I asked the question how far it could be expected to go before an organism would become irredeemably frail through loss of all its defences against the slings and arrows of nature. I was told that certainly there was a risk of ending up with an organism that died “the moment you looked at it.”
JVCI-syn3.0 doesn’t do that. It seems to thrive, given the right nutrients and environment: a colony doubles in size every three hours. The JCVI scientists, led by the formidably gifted biologists Clyde A. Hutchinson and Hamilton Smith, stripped down the M. mycoides genome by trial and error, having first discovered that their attempts to design such a genome on the drawing board didn’t work. “Our current knowledge of biology is not sufficient to sit down and design a living organism and build it,” Venter admitted to Science, where their work is published.
So instead they developed methods for chopping up the bacterium’s genome and removing segments piece by piece, allowing them to see which genes were essential and which were not. Their starting point was not natural M. mycoides but an earlier…