Friday, April 1, 2016

‘Minimal’ Cell Raises Stakes in Race to Harness Synthetic Life

Genomics entrepreneur Craig Venter has created a synthetic cell that contains the smallest genome of any known, independent organism. Functioning with 473 genes, the cell is a milestone in his team’s 20-year quest to reduce life to its bare essentials and, by extension, to design life from scratch.

Venter, who has co-founded a company that seeks to harness synthetic cells for making industrial products, says that the feat heralds the creation of customized cells to make drugs, fuels and other products. But an explosion in powerful ‘gene-editing’ techniques, which enable relatively easy and selective tinkering with genomes, raises a niggling question: why go to the trouble of making new life forms when you can simply tweak what already exists?

Unlike the first synthetic cells made in 2010, in which Venter’s team at the J. Craig Venter Institute in La Jolla, California, copied an existing bacterial genome and transplanted it into another cell, the genome of the minimal cells is like nothing in nature. Venter says that the cell, which is described in a paper released on 24 March inScience, constitutes a brand new, artificial species.

“The idea of building whole genomes is one of the dreams and promises of synthetic biology,” says Paul Freemont, a synthetic biologist at Imperial College London, who is not involved in the work.

The design and synthesis of genomes from scratch remains a niche pursuit, and is technically demanding. By contrast, the use of genome editing is soaring — and its most famous tool, CRISPR–Cas9, has already gained traction in industry, agriculture and medicine, notes George Church, a genome scientist at Harvard Medical School in Boston, Massachusetts, who works with CRISPR. “With much less effort, CRISPR came around and suddenly there are 30,000 people practising CRISPR, if not more.”

Microbiologists were just starting to characterize the bacterial immune system that scientists would eventually co-opt and name CRISPR when Venter’s team began its effort to whittle life down to its bare essentials. In a 1995 Science paper, Venter’s team sequenced the genome of Mycoplasma genitalium, a sexually transmitted microbe with the smallest genome of any known free-living organism3, and mapped its 470 genes. By inactivating genes one by one and testing to see whether the bacterium could still function, the group slimmed this list down to 375 genes that seemed essential.

by Ewen Callaway, Nature |  Read more:
Image: homas Deerinck and Mark Ellisman/NCMIR/UCSD