Organisms created with synthetic DNA pave way for entirely new life forms
E coli microbes have been modified to carry an expanded genetic code which researchers say will ultimately allow them to be programmed
By Ian Sample
Jan 24 2017
From the moment life gained a foothold on Earth its story has been written in a DNA code of four letters. With G, T, C and A – the molecules that pair up in the DNA helix – the lines between humans and all life on Earth are spelled out.
Now, the first living organisms to thrive with an expanded genetic code have been made by researchers in work that paves the way for the creation and exploitation of entirely new life forms.
Scientists in the US modified common E coli microbes to carry a beefed-up payload of genetic material which, they say, will ultimately allow them to program how the organisms operate and behave.
The work is aimed at making bugs that churn out new kinds of proteins which can be harvested and turned into drugs to treat a range of diseases. But the same technology could also lead to new kinds of materials, the researchers say.
In a report published on Monday, the scientists describe the modified microbes as a starting point for efforts to “create organisms with wholly unnatural attributes and traits not found elsewhere in nature.” The cells constitute a “stable form of semi-synthetic life” and “lay the foundation for achieving the central goal of synthetic biology: the creation of new life forms and functions,” they add.
Floyd Romesberg and his team at the Scripps Research Institute in California expanded the genetic code from four letters to six by adding two new molecules they call X and Y and adding them to the bugs’ genetic makeup. The microbes are modified to absorb the new genetic material which the scientists make separately and then feed to the cells.
The need to supply the bugs with the X and Y molecules is meant to ensure that the cells will die should they somehow get out of the lab. But Romesberg said that despite the protective measure, he still gets asked if he has seen Jurassic Park. In the 1993 movie, Jeff Goldblum questions whether the park’s dinosaurs might breed in the wild despite the failsafes built into their genetic makeup. “What the movie depicted is very different to our failsafe,” Romesberg said. “Our failsafe is based on the availability of X and Y and the cell could never make them.”
“In addition, evolution works by starting with something close and then changing what it can do in small steps. Our X and Y are unlike natural DNA, so nature has nothing close to start with. We have shown many times that when you do not provide X and Y, the cells die, every time,” he added.
It is not the first time Romesberg has made microbes with an expanded genetic alphabet. In 2014, he announced the first such organisms, but these were sickly and soon died out. He compares the situation to having proved he could generate electricity, but not put it to good use. “We demonstrated that you could throw the switch and the light would go on, but then it would quickly go out,” he said.