Frances Arnold “Bacterial Builders” – Giving Evolution a Little Nudge
Chemistry is on the verge of a bacterial revolution. Fastforward into the future, and you might find that the polyester in a Hawaiian shirt, the rubber in a new set of tires, or even Grandma’s blood pressure medication was made in much the same way beer is brewed: by harnessing the powers of the tiny unicellular organisms that are ubiquitous in our world.
Sound far-fetched? The yeast that have been used to make beer for hundreds of thousands of years, as well as some even smaller bacteria, are already being co-opted to create materials like spider silk, biodegradable plastics, vitamins, insulin, and human growth hormone. Scientists perform such transformations by pulling the genetic material out of another organism—a spider, for example—and inserting it, with a few edits and additions, into a microorganism. When the modified organisms return to their normal microbial business, they will also churn out what their new DNA tells them.
While effective, the method works only if a living creature already exists with DNA encoded for the desired product and if the DNA can be appropriately modified to be read by the microbes. But what are scientists to do if they want bacteria to make something that is not already a natural, organic, preexisting compound?
They give evolution a little nudge.
One way to do that is through a process familiar to breeders of all sorts of domesticated animals. When ancient humans wanted wolves as hunting companions, for instance, they picked the friendliest wolf cubs and kept breeding them and their friendliest offspring until they arrived at man’s best friend, in all its different forms.
The difference is that today when researchers want new breeds of bacteria, they can deliberately tweak the genes directly instead of just waiting for useful mutations to arrive by accident. It is a process known as directed evolution, first developed by Caltech chemical engineer Frances Arnold in the early 1990s. In the years since, she and her colleagues have created genes that encode not just better versions of enzymes that already exist but genes that compel the organisms to perform a variety of chemical feats never before seen in nature.
“You mutate a gene, see which progeny have the properties that you want, pick the one or ones that you like, and repeat the process,” says Arnold. “You keep doing it over and over again until they do what you want them to. The great thing about bacteria is that you can do this very quickly because bacteria reproduce rapidly. A generation can be as short as a few days, sometimes even shorter.” In 2016, Arnold and her group announced that they had used directed evolution to create enzymes that enable bacteria to bond silicon atoms to carbon atoms. Though silicon-carbon bonds are common in synthetic materials (think silicone caulk), such bonds in organic materials had previously only been created by chemists.
Read Full article HERE. Source & Credit @ Caltech.