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.