Scientists have succeeded in growing diverse populations of gut bugs in the laboratory that closely mimic those in the body.
The friendly microbes, trillions of which live in our intestines, are known to protect against inflammatory conditions such as Crohn's and may also help prevent excessive weight gain.
Until now researchers have not been sure that lab cultures of bacteria accurately mirror those found in an individual patient's gut.
Scientists used the latest technology to identify the genetic fingerprints of microbes grown from stool samples.
They found it was possible to grow most of the different groups of intestinal bacteria found in an individual patient in a laboratory petri dish.
Further studies on mice showed that both "natural" and cultured samples of the bacteria behaved the same way in response to dietary changes.
"This research helps set up a discovery pipeline in which we can deliberately manipulate collections of human intestinal microbes from people of different ages and cultures who are either healthy or sick," said study leader Professor Jeffrey Gordon, from Washington University School of Medicine in St Louis, Missouri, US.
The findings are published in an online early edition of the journal Proceedings of the National Academy of Sciences.
Prof Gordon said in future it may be possible to obtain personalised microbial communities from people around the world who consume different diets, and from individuals who are obese, malnourished, or suffering from conditions such as Crohn's disease.