Nature reports:

Most studies on how humans acquire their microbiomes have focused on people’s first contact with microbes: through their mums. “It’s key to providing a microbial starter kit,” says Hilary Browne, a microbiologist at the Wellcome Sanger Institute in Hinxton, UK.

To examine how and why this starter kit changes over a person’s life, a team led by microbiome researchers Mireia Valles-Colomer and Nicola Segata at the University of Trento, Italy, analysed DNA from nearly 10,000 stool and saliva samples from people all over the world, from rural villages in Argentina to a city in China to populations in Europe and North America. The researchers then looked for overlap in the strains of microbes found in the guts and mouths of family members, partners, housemates and other social contacts.

The analysis confirmed the strong link between the microbiomes of mothers and those of their children, particularly early in life. During an infant’s first year of life, half of the microbial strains in their guts were shared with their mothers. The extent of overlap decreased as children aged — but did not vanish. Older people, aged 50–85, still had gut microbe strains in common with their mothers.

Other family members were also an important source of gut microbes. After the age of 4, children shared similar numbers of microbe strains with their father as with their mother. And twins who moved away from each other shared fewer gut microbes the longer they had lived apart. Sharing occurred even between households in several of the rural-living groups: people from separate households in the same village tended to have more overlap in gut microbes than did people from different villages. [Continue reading…]