Cohabiting twins can share microbial gut strains for decades

Researchers at the University of Alabama at Birmingham, showed the existence of shared gut microbial strains in twins, even after years post separation.
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What is already known on this topic
The infant’s intestinal microbiota are believed to be transmitted to the child from the mother at birth. The early gut colonizers, like Actinobacteria and Bacteroidia create the microbial reservoir in the gastrointestinal tract that later develops into a stable gut bacterial community. However, how individual gut microbiome composition endures and stays stable over time is unknown.

What this research adds
The researchers, using two metagenomics sequencing databases analysed the stability of certain microbial strains between pairs of child twins living together and adult twins up to 80 years of age, who lived apart from 1 to 59 years.

Certain gut microbial populations can be shared between twins for years after living apart, however long-term changes in the host environmental conditions can impact the stability and composition of the gut microbial community.

Do child twins share microbial strains “fingerprint” in their guts? Hyunmin Koo and colleagues, using a genomic strain-tracking bioinformatics tool developed at the University of Alabama at Birmingham, showed the existence of shared gut microbial strains in twins, even after years post separation.

The team had already developed and applied the strain-tracking program to their research. In 2017 they found that fecal donor microbes for recurrent C. difficile infection remained in the recipient for months after fecal transplant, and more recently the researchers have found that microbial strains are unique between individuals and have tracked related microbiota changes in individuals following antibiotic treatments.

The current study used metagenomics sequencing databases from fecal samples of 8 child twin individuals and 50 adult twin individuals. Twins have a common mother and probably live in similar environmental conditions throughout childhood, therefore the researchers hypothesized that they might also share certain gut microbial strains. Indeed, they found significantly more shared strain pairs in child twins who still lived together, as compared with adult twins after living apart for periods of time.

For the most of children twin sets (3 out of 4) considerable strain sharing was found for several microbes, notably B. vulgatus and Alistipes putredinis.

Among the adult twins, those who had lived apart less than 10 years shared significantly more related strain pairs than twins living apart for longer periods, from 10 to 60 years.

Interestingly, 80-year-old twins who had lived together for 79 years then were apart for 1 year showed the highest number of related strain pairs consisting of B. vulgatus, Eubacterium eligens and Bifidobacterium adolescentis, across all adult twins. The next highest numbers of related strain pairs were found in 56-year-old twins who had lived together for 51 years then apart for five years, in 73-year-old twins who lived together for 66 years and then apart for seven years, and in 36-year-old twins separated for 19 years. Single-shared strains were seen in three twin sets who had lived apart between 22 to 54 years, but these sporadic shared strains did not show a correlation with the length of living apart.

These results support that microbial strains in the gut of certain individuals remain for longer times than previously thought, possibly up to a decade. However, this study is limited by the availability of a single analysis time point for the adult twins, furthermore metadata information about personal and medical habits known to alter the gut microbial community was missing. In summary, while certain gut microbial strains can be stable in people during aging, environmental changes such as antibiotics and new diets occurring throughout the years in life, can disrupt the stable composition of the gut microbial community essential in human health.