November 7, 2011
Commanding Yeast Genes With Computers
Scientists in Switzerland have managed to form a “feedback loop” between a computer and a common yeast, precisely controlling the switching on and off of specific genes. This could herald the ability to control biological processes, such as creating biofuel from microbes, Jason Palmer of BBC News reports.
“The neat thing about this is that there are many people who have tried to do things like this by, for example, coding in the cell itself a synthetic circuit, putting genes and mechanisms in the cell,” said senior author John Lygeros, of the Automatic Control Laboratory at the Swiss Federal Institute of Technology Zurich. “That´s had limited success up to now.”Lygeros and his fellow researchers began with the yeast Saccharomyces cerevisiae, a strain of yeast used in brewing and baking since ancient times.
A study in the journal Nature Biotechnology in 2002 found that when S. cerevisiae is exposed to light, a molecule called phytochrome within it can switch forms. Red light converts it to an “active form” and a deeper red reverts the switch. This can start or stop the genetic process that results in the production of a given protein.
Taking advantage of this process to ensure that when the yeast was producing that protein, corresponding to the gene being switched on, it could be tracked by using a “reporter” molecule that itself fluoresces.
This allowed the team a full loop of control. Upon shining red light in, they could track how much a population of yeast cells was expressing the gene, and apply the deeper red to curb that gene expression.
The process is not simply an on-off switch, Lygeros explained to Palmer. “Experimentally, it s a fairly challenging thing to do. The fluorescence is not the only thing - there are half a dozen chemical reactions involved in this process.”
This research adds to a growing amount of knowledge in which the machinery within life can be bent to the will of scientists. Most recently, researchers at the University of San Francisco showed that a substantially similar approach could direct a prescribed amount of a protein to the cell wall.
This research will aid many aspects of biologic study and help us better understand cell signaling.
Such methods are helping to complement time-honored but labor-intensive genetic trickery to accomplish similar goals, Lygeros explained. “It´s quite difficult to engineer synthetic circuits that do something robustly in the cell, and the hope is that by augmenting this with external signals, you can get them to behave better,” he said.
“That for example may have applications in biofuel production, or antibiotic production, where they use genetically engineered organisms to increase the yields of reactions.”
Image Caption: Sacharomyces cerevisiae cells in DIC microscopy. Imaging was performed with the Olympus BX61 microscope and a UPlanSApo 100Ã NA 1.40 oil immersion objective (Olympus). Pictures were acquired at room temperature in synthetic complete medium with a camera (SPOT; Diagnostic Instruments, Inc.) using MetaMorph software (MDS Analytical Technologies). Credit: Masur/Wikipedia
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