One of biology’s biggest achievements of 2016 was intentionally as small as possible: building a bacterium with only 473 genes. That pint-size genetic blueprint, the smallest for any known free-living cell, is a milestone in a decades-long effort to create an organism containing just the bare essentials necessary to exist and reproduce. Such “minimal genome” cells might eventually serve as templates for lab-made organisms that pump out medicines, make innovative chemicals for industry and agriculture, or churn out other molecules not yet imagined. The project also identified genes crucial for the microbe’s survival yet largely unfamiliar to science, highlighting major gaps in researchers’ grasp of life’s playbook.
The newly engineered bacterium was praised as a technical triumph. In 2010, researchers at the J. Craig Venter Institute in La Jolla, Calif., had stitched together a copy of the entire genome of the bacterium Mycoplasma mycoides and popped it into the cell of another bacterium whose genome had been removed. But that “synthetic cell,” dubbed JCVI-syn1.0, contained a full copy of an existing genome. With more than 1 million chemical building blocks of DNA, including 901 genes, it was far from minimal.