Washington, Sep 6 (IANS): Lab mice receiving gut bacteria from obese humans are likely to put on more weight compared to those given bacteria from the gut of lean humans, US researchers say.

The findings demonstrate the transmission of the physical and metabolic traits via gut microbes and represent an important step towards developing anti-obesity treatment with bacteria, Xinhua reported, citing the Science journal.

Researchers from the Washington University recruited four human twin pairs - two obsese and two lean - and transferred the gut microbiota from each of them into the guts of germ-free mice that had been raised under sterile conditions.

They found that the recipients of the obese twins' microbiota gained more fat than the recipients of the lean twins' microbiota when the mice were fed a standard diet.

"This wasn't attributed to the differences in the amount of food they consumed, so there was something in the microbiota that transmitted this trait. Our question became: What were the components responsible," said Jeffrey Gordon, director for the Centre of Genome Sciences and Systems Biology at Washington University.

Analysis of the bacteria showed that bacteroidetes phylum could pass from the lean mice and colonise the obese mice, suggesting that these were largely responsible for protection against weight gain.

According to the researchers, none of the bacteria from the obese mice could invade the lean mice to make them accumulate fat.

To learn more, the researchers formulated diets for the mice that were representative of modern Western diets - low in fibre and high in saturated fats - and found both the obese and lean mice appeared to be unaffected by the others' gut microbes.

However, when the animals were given the "healthier", high-fibre and low-fat human diet, the results were the same as before.

The findings indicated that more complex interactions between diet, body mass and gut microbiota underlie human metabolic disturbances than researchers have appreciated.