Bioengineers around the world have been working to create plastic-producing microbes that could replace the petroleum-based plastics industry. Now, researchers have overcome a major hurdle: getting bacteria to produce polymers that contain ring-like structures, which make the plastics more rigid and thermally stable. Because these molecules are usually toxic to microorganisms, the researchers had to construct a novel metabolic pathway that would enable the E. coli bacteria to both produce and tolerate the accumulation of the polymer and the building blocks it is composed of. The resulting polymer is biodegradable and has physical properties that could lend it to biomedical applications such as drug delivery, though more research is needed.