Hinxton, UK – A recent study has uncovered the evolutionary history of the simple yeast, the organism that gives us fermented beer and risen bread. Using sequencing technology researchers have, for the first time, shown that humans have tamed yeast on multiple occasions in their history. More dramatically, the research links two important projects in biomedical research and in the work of the Wellcome Trust Sanger Institute. Yeast was the first genome completed at the Sanger Institute in 1996 and the research published today has played an essential role in developing the principles and tools for The 1000 Genomes Project launched in 2007.
From cell division to cancer, yeast has helped researchers to grasp biological principles and today’s results continue that tradition. But has our long association with yeast made it too domesticated? Does the highly selected yeast we now produce for laboratory experiments in any way influence the outcome of scientific research?
The new research looked at the genome sequences of 70 samples of yeast from around the world. Ed Louis, a professor of genome dynamics at the Institute of Genetics at The University of Nottingham explains: “We didn’t know much about the evolution of yeast and how much influence we had over the centuries by highly selecting for brewing, baking and laboratory experiment properties. It remains to this day one of the best models for evolutionary studies.”
Until now little has been known about the evolutionary processes taking place within populations and different strains of domesticated yeast. The team examined genome sequences from Saccharomyces cerevisiae (S. cerevisiae), commonly used in laboratory research, baking, wine making and in the production of sake. These were compared with its closest relative, Saccharomyces paradoxus (S. paradoxus) isolates, found in oak tree bark.
The project did not sequence the genome of each strain in great detail: to improve efficiency, each was sequenced to a depth that would allow the team to gather DNA sequence differences between the strains and, where sequence was poor or lacking, to impute the probable sequence differences between them. The techniques and the results have served as proof of principle for the methods used in The 1000 Genome Project, the three-year programme to decode genomes of 1000 people.
“We have been able to use the amazing power of modern DNA sequencing to obtain an unprecedented picture of the way the genes in this organism vary, and how it evolved,” says Dr Richard Durbin, Senior Investigator at the Wellcome Trust Sanger Institute and co-leader of The 1000 Genomes Project. “The tools we developed to study yeast are now being applied to the human genome, to help identify genetic variants that are involved in disease.”
The genome of S. cerevisiae – it is about 12 million letters of genetic code – was sequenced by an international consortium including the Wellcome Trust Sanger Institute – the process took years to complete, with the research being published in 1996. Using the next-generation sequencing technologies now available, researchers can complete a sequence of this size and quality in little over half an hour.
“Model organisms such as yeast, worm, fly and mouse have been and will continue to be essential to biological exploration,” continues Dr Durbin, whose own work was instrumental in interpreting the genome of the nematode worm and in the Human Genome Project.
The use of yeasts in cooking and brewing has led to suggestions that humans might have cultivated selected strains for these purposes. In at least some cases, nature still has a lead. The research team mention recent findings, in Malaysia, of chronic intake of alcoholic nectar from Bertram palms by wild tree shrews: fermented beverages seem popular with other primates and not only humans.