Strong ties: who do we share our microbiome with?

The human body is home to thousands of species of bacteria – researchers call this our microbial landscape. At birth, we pick up a large portion of our bacterial makeup from our mothers; as we age, our microbial makeup changes and diversifies.

Image Source: Jeni Wightman’s installation “Microbial Landscape Paintings: Seasonal Color via Species Succession” linked here.

A recent large-scale study explored how microbes are shared between people. The researchers analysed 10,000 samples across Tanzania, China, Ghana, USA, and Italy. They calculated the number of bacterial strains shared by pairs of people, determining the amount of strain sharing between mothers and infants, household members, adult twin pairs, and across villages. 

They found that infants and their mothers had the highest strain sharing and that the level of strain sharing depended on the route of delivery. Vaginally delivered infants shared more bacterial strains with their mothers than those delivered through C-sections. The amount of strain sharing between infants and their mothers decreased with time, and it approached strain sharing levels observed between household members.

Using adult twins, researchers found that strain sharing decreased with the number of years lived apart, suggesting contributions from the environment. They also found that identical twins shared more microbial strains than fraternal twins, suggesting the role of genetics. When studying microbial sharing within villages, strain sharing appeared to occur through contact between villagers. Interestingly, the researchers pinpointed distinct bacterial strains that were found to be most efficiently transmitted. This finding inspires work on how microbiome sharing can contribute to the spread of disease.