A new approach to materials synthesis has shown promise in the creation of living elements. Researchers at MIT have influenced E. coli bacterial cells to produce biofilms that could incorporate nonliving materials such as gold nanoparticles and quantum dots. They worked with E. coli because it naturally produces biofilms that contain “curli” fibers — amyloid proteins that help E. coli attach to surfaces. Each fiber is made from a repeating chain of identical protein subunits (CsgA), which can be modified by adding peptides. They programmed the cells to produce various types of curli fibers, ultimately allowing them to control the biofilms’ properties and create gold nanowires, conducting biofilms and films studded with quantum dots. They also engineered the cells to communicate with each other and change the composition of the biofilm over time. Combining the advantages of live cells with those of nonliving cells, these living materials also have the potential to emit light, conduct electricity, produce complex biological molecules and span multiple length scales. “Our idea is to put the living and the nonliving worlds together to make hybrid materials that have living cells in them and are functional,” said researcher Timothy Lu, assistant professor of electrical engineering and biological engineering at MIT. “It’s an interesting way of thinking about materials synthesis, which is very different from what people do now … usually a top-down approach.” In the future, he added, the technique could be used to design complex devices, such as solar cells, self-healing materials and diagnostic sensors. “It’s a really simple system, but what happens over time is you get curli that’s increasingly labeled by gold particles. It shows that, indeed, you can make cells that talk to each other, and they can change the composition of the material over time,” Lu said. “Ultimately, we hope to emulate how natural systems, like bone, form. No one tells bone what to do, but it generates a material in response to environmental signals.” The work was funded by the Office of Naval Research, the Army Research Office, the National Science Foundation, the Hertz Foundation, the Department of Defense, the National Institutes of Health and the Presidential Early Career Award for Scientists and Engineers. The research is published in Nature Materials (doi: 10.1038/nmat3912). For more information, visit: www.mit.edu.