Fully Functional Bacterial Cell Thrives with Synthetic Genome

Craig Venter Institute (San Diego, CA, and Rockville, MD, USA) synthesized the 1.08 million base pair (bp) chromosome of a modified Mycoplasma mycoides genome. To prepare the accurate, digitized M. mycoides genome, the investigators designed 1,078 specific cassettes of DNA that were 1,080 base pairs long. These cassettes were designed so that the ends of each DNA cassette overlapped each of its neighbors by 80 bp. The cassettes were made by the DNA synthesis company, Blue Heron Biotechnology (Bothell, WA, USA).

A three-stage process using a previously described yeast assembly system was employed to build the genome using the 1,078 cassettes. The first stage involved taking 10 cassettes of DNA at a time to build 110 10,000-bp segments. In the second stage, these 10,000-bp segments are taken 10 at a time to produce 11 100,000-bp segments. In the final step, all 11 of the 100-kb segments were assembled into the complete synthetic genome in yeast cells and grown as a yeast artificial chromosome.

The complete synthetic M. mycoides genome was then isolated from the yeast cells and transplanted into Mycoplasma capricolum recipient cells that lacked restriction enzyme genes. The synthetic genome DNA was transcribed into messenger RNA, which in turn was translated into new proteins. The M. capricolum genome either was destroyed by M. mycoides restriction enzymes or was lost during cell replication. After two days viable M. mycoides cells, which contained only synthetic DNA, were clearly visible on Petri dishes containing bacterial growth medium.

Details of the project were published in the May 20, 2010, online edition of the journal Science. Here, the investigators assigned the name Mycoplasma mycoides JCVI-syn1.0 to the synthetic cell. They termed it the proof-of-principle that genomes can be designed in the computer, chemically made in the laboratory, and transplanted into a recipient cell to produce a new self-replicating cell controlled only by the synthetic genome.

Contributing author Dr. Clyde A. Hutchison, a senior researcher at the J. Craig Venter Institute, said, "To me the most remarkable thing about our synthetic cell is that its genome was designed in the computer and brought to life through chemical synthesis, without using any pieces of natural DNA. This involved developing many new and useful methods along the way.”

Related Links:
J. Craig Venter Institute
Blue Heron Biotechnology