A worldwide network of geneticists are trying to artificially engineer the world’s first complex living organism—their own version of winemaking’s workhorse yeast, Saccharomyces cerevisiae.
A dozen labs are simultaneously sequencing the 16 chromosomes that house the 12 million base pairs (the building blocks of any DNA sequence) that will make this fully synthetic yeast cell, affectionately known by the team as Yeast 2.0. And they’re more than halfway through with the project. Chromosome No. 3 had been fully synthesized as of March, according to project leader Jef Boeke, a professor at Johns Hopkins University. The remaining 15 chromosomes have been assigned, and some of those are more than halfway through their sequencing.
Why a yeast cell? And why Saccharomyces cerevisiae? While it's considered a “complex organism,” unlike the simple parasitic bacterium scientists created in 2010, it is still one of the simpler complex organisms—not as complex as a fruit fly, for example. Plus, yeasts have innumerable applications in the world of biofuels, pharmaceuticals and, of course, wine production.
One lab, at Adelaide's Macquarie University, is working in conjunction with the Australian Wine and Research Institute (AWRI), sharing both manpower and funding in an effort to complete chromosome No. 14.
Does this mean we'll soon see synthetic yeasts being used in winemaking? It's unlikely. “It is important to emphasize that Yeast 2.0 will not lead to the use of genetically modified or synthetic yeast in winemaking, at least in Australia, as the policies are very clear on that front,” said Dan Johnson, managing director of AWRI, at a recent symposium in Australia on the Yeast 2.0 project.
To ensure that this remains the case, controls are encoded. "These are lab-adapted strains that have an auxotrophic mutation," said Boeke. An auxotrophic mutation means an organism cannot synthesize a particular organic compound required for its growth—those compounds have to be regularly supplied by the scientists. "They are not very successful at reproduction, yet it is theoretically possible that they could mate with wild yeast strains at some low rate of occurrence, so we are installing a series of safety switches to prevent any multiplication in the wild.”
So if the end game isn’t patentable, boutique organisms, then what is the goal? Johnson pointed out that scientists have increasingly been trying to understand how yeasts metabolize grape juice and produce complex flavors. "Yeast 2.0 will yield this type of fundamental understanding of yeast in a laboratory environment. This information can be applied to achieve a better level of control over the fermentation process.” All of which means that Yeast 2.0 is an attempt to understand the interaction and metabolic process of Saccharomyces cerevisiae at a genetic level. Sometimes the best way to understand how an organism works is to build it from scratch.
Boeke expects the project will be finished in two to three years.