Genome Res. doi:10.1101/gr.107987.110 (2010)

In bowel diseases, the balance of the gut's microbial species, which number more than 1,000, can be thrown off. Researchers have speculated that transplanting a collection of microbes from the guts of healthy individuals into those of patients could be therapeutic.

Chaysavanh Manichanh at the University Hospital Vall d'Hebron Research Institute in Barcelona, Spain, and her colleagues transplanted gut microbes between rat strains. Genetic analysis of the rats' intestinal microbial populations revealed that the bacterial composition in recipient animals closely resembled that of the donors. The effect persisted three months after transplantation.

First treating the recipient animals with antibiotics, however — a step widely thought to make way in the gut for the incoming microbes — did not improve how well the donor colony took root.