Scientists from the University of California, San Diego, this week report data demonstrating that live gut bacteria from mouse hosts — and potentially humans — can be engineered to deliver a therapeutic payload. Efforts to develop live bacterial therapeutics, which would engraft in the gut and provide persistent beneficial functions to the host, have been unsuccessful thus far because the gut microbiome is hostile to non-native bacterial organisms, making colonization difficult. To overcome this, the researchers engineered Escherichia coli that had been isolated from mouse stool cultures to express functional genes. As reported in Cell this week, the reintroduction of the strains to mice led to perpetual engraftment in the animals' intestines and, importantly, to durable functional changes including ones that affected diabetes progression. The team also showed that human-derived E. coli could be modified for transgene delivery. "If the engineered native bacteria strategy is successfully developed and translated to humans, it has the potential to introduce novel, curative biotherapeutics that improve treatment of chronic diseases without relying on patient compliance," the study's authors write.