Yeast, the sugar-gobbling microorganism that’s filled our bellies with beer and bread for millennia, has a new, increasingly important, role to play in society: serving as a therapeutic drug factory.

In August, scientists announced they had genetically engineered yeast to produce the painkiller hydrocodone, and even before that breakthrough, modified yeast churned out the anti-malarial drug artemisinin.

Now, scientists have customized yeast to create THC (the marijuana chemical that pr