It turns out that roommates can share more than just their outfits. Research out this week shows that people living in the same home share many of the same bacteria found in their bodies.
Scientists at the University of Trento in Italy examined the gut and mouth microbiomes of over 400 people. People who lived together tended to have more similar strains of bacteria than people in the same community who didn’t live together, they found—with about a quarter of their microbiomes being shared. Romantic couples who lived together had even more mouth bacteria in common, likely due to more intimate behaviors, such as kissing.
“These findings extend our understanding of microbiome spread and its potential consequences for human health,” the researchers wrote in their paper, published Monday in the journal Cell Press Blue.
Bacterial roommates
Our bodies are teeming with microbial communities, known as microbiomes. These microbiomes are vital, though we’re still trying to figure out all the different ways they can affect our health.
Research has shown that the composition of our microbiomes is heavily shaped by our early life experiences and environments. According to the researchers, there’s a lot less known about exactly how our microbiomes can shift later on in life.
“We know that diet and other lifestyle factors can change our microbiome, but these factors are acting on the microbes that are already within us,” said senior author Nicola Segata, a computational biologist at the University of Trento, in a statement from the university. “It doesn’t solve the question about where the microbes are coming from.”
Segata and his team analyzed genetic data from the gut and oral microbiomes of 430 people living in 207 households across Italy and Fiji. They specifically focused on the strains of bacteria found within these microbiomes.
Overall, the researchers found, roommates shared 19% of their gut microbiome strains and 26% of their mouth bacteria strains, whereas non-roommates in the same community only shared 6% of their gut microbiomes and 0% of their mouth microbiomes. Romantic partners, meanwhile, shared about 44% of their mouth microbiome strains.
What this means
The findings indicate that our environments still play a significant role in shaping our microbiomes even as we age, if only to a certain extent.
And though most of the bacteria that live in our bodies are either harmless or beneficial, the bacteria we share with others might be more prone to causing or worsening disease risk, the researchers say. They found the most transmissible strains of gut bacteria were linked to type 2 diabetes or poor heart health, for instance, while some of the most transmissible strains in the mouth were linked to colorectal cancer or opportunistic infections (infections that stir up trouble when the immune system is weakened).
“It’s difficult to speculate why this is, but it might be a reflection of their ability to withstand stress,” said lead researcher Vitor Heidrich, a fellow computational biologist at the University of Trento, in a statement. “The same traits that help them survive the journey between humans may also allow them to thrive in the inflammatory conditions associated with disease.”
The lessons learned from this and similar research will ideally help us better understand the microbiome and how to change it for the better. And in the meantime, it might either be disgusting or heartwarming to know that we share even more than assumed with our roommates and loved ones.
