The bacteria growing on stacks of petri dishes in Daniel Gibson’s lab are the first living creatures with a completely artificial genome. The microbes’ entire collection of genes was edited on a computer and assembled by machines that create genetic fragments from chemicals and by helper cells that pieced those fragments together. Gibson hopes that being able to design and create entire genomes, instead of just short lengths of DNA, will dramatically speed up the process of engineering microbes that can carry out tasks such as efficiently producing biofuels or vaccines.
Until last year, biologists hadn’t been able to make large enough pieces of DNA to create an entire genome; though living cells routinely make long stretches of DNA, a DNA synthesis machine can’t do the same. In May, Gibson and his colleagues at the J. Craig Venter Institute announced their solution to this problem. Gibson used yeast cells to stitch together thousands of fragments of DNA made by a machine, pooled the longer pieces, and repeated the process until the genome was complete. Next he inserted the genome into bacterial cells that were about to divide and grew the bacteria in a medium hostile to all cells except the ones harboring the synthetic genome.