DNA of bacteria can pass a trait to offspring in a way similar to the parents' own DNA, the findings showed. It is already known that traits such as eye colour and height are passed from one generation to the next through the parents' DNA.

"This suggests we may need to substantially expand our thinking about their (bacteria') contributions, and perhaps the contributions of other microorganisms, to genetics and heredity," said co-senior author Herbert Virgin IV from Washington University School of Medicine in St Louis. Most bacteria are commensal, which means they do not cause harm and often confer benefits.

This is the first study to show that bacterial DNA can pass from parent to offspring in a manner that affects specific traits such as immunity and inflammation, the researchers noted.

The researchers linked commensal bacteria in mice to the animals' susceptibility to a gut injury. Mice with certain inherited bacteria are susceptible to the injury, which is caused by exposure to a chemical.

Female mice pass the bacteria to their offspring, making them vulnerable to the injury. Others carrying different bacteria are less susceptible. The study appeared online in the journal Nature.

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