Diabetes could be cured using poo from healthy people.
A study discovered that microscopic organisms transplanted into mice stops the condition from progressing and the technique involves engineering E. coli bacteria from samples of excrement.
Experts say that the development could end the need for insulin injections for those who have the disease.
Professor Amir Zarrinpar, from the University of California, said: "We have engineered these bacteria to become factories that can live in our microbiome and potentially produce medicines.
"All I can say to the non-native bacteria is good luck."
The method could also be capable of treating a range of gut conditions, ranging from obesity to irritable bowel syndrome.
Professor Zarrinpar added: "This can influence so many different chronic and genetic diseases."