Dogs are even more a member of the family than you thought

We’re ten times as much bacteria as we are human, if you go by cell numbers. But we don’t all have the same mix of microbes coating us inside and out. Family members tend to share bacterial communities with each other. No surprise there, since people living in close contact tend to interact physically and to eat the same foods. What may surprise you is to know that the microbe similarities extend to pets.

Researchers led by Rob Knight and Se Jin Song of the University of Colorado, Boulder compared the microbiota in families consisting of heterosexual couples living with or without their biological children and with or without dogs. Fecal, oral and skin swabs were taken from all humans and dogs in the study. The bacterial makeup of the humans was more similar to that of their family members than to unrelated people. The microbiota of humans was also more similar to that of their own pets than to other people’s dogs. In addition, adults who owned dogs had a greater diversity of skin bacteria.

Here’s the interesting part. A couple shared more skin bacteria with each other if they lived with a dog. There was a much smaller effect if the couple had children. It seems that dogs are better at transferring bacteria around than kids.

What’s behind all this? The authors note that dogs tend to have a much greater variety of skin/fur bacteria than humans do. If the dogs were passing some of those microbes on to their people, that would significantly alter the composition of the humans’ skin biota, but in a way that affected all family members equally. 

Now if you'll excuse me, I have to give my dog a bath.

Song, S., Lauber, C., Costello, E., Lozupone, C., Humphrey, G., Berg-Lyons, D., Caporaso, J., Knights, D., Clemente, J., Nakielny, S., Gordon, J., Fierer, N., & Knight, R. (2013). Cohabiting family members share microbiota with one another and with their dogs eLife, 2 DOI: 10.7554/eLife.00458.