Moms are great. They teach you to walk. They teach you to wash your hands so you won’t get sick. They teach you not to put cockroaches in your mouth so they won’t get sick. They teach you to never drink milk without smelling it first. And never drink it from the jug! We get a lot from our moms. Without them we’d pretty much be unable to function as humans. And without them, we’d be unable to function as ecosystems.
You probably know that you get half of your genes from your mom and half from your dad. You might know that you get all of your mitochondrial genes from your mom. But what you don’t know you get most of your bacterial genes from your mom as well. And this makes up the majority of the genes within your body. You have 10 bacterial cells for each human cell in your body but you have about 100 bacterial genes for every human gene.
Like most symbiotic science, we haven’t know this for long. We used to think the uterus was sterile and that the first dose of bacterial companions came with birth. The assumption kinda went, “Bacteria are bad. Baby is fragile. Womb is safe. No bacteria in womb, keep baby safe”. We used to think we got all our bacteria from the vaginal canal. A large number of the first colonizers for a newborn come from there. You can see this in a distinct difference in the levels of bacteria between deliveries via C-section and natural birth. This has made a case against C-sections, supported by a connection between this reduced level of bacteria and an increased likelihood of developing allergies.
(Check out this MinuteEarth video on pets, bacteria, and birth)
Think of it as a Fetal Microbiota Transplant. This transfer is ongoing, from conception to birth to infancy and childhood. We get bacteria through the placenta, through the vaginal canal, through breastfeeding and even through kissing. The connection between romantic kissing has been recently characterized as much larger than we originally thought. And the similarity in bacterial composition of romantic partners is incredible.
What’s interesting is that romantic kissing is thought to be a transposition of the mother-child kissing which has been present in our species much longer. And if kissing started that way, could it be that it had a benefit of microbial transmission? And do these benefits of donating bacteria apply to couples too?
(Check out this NPR article on the 80 million bacteria in a romantic kiss)
But you and your bacteria aren’t paired for life. Your microbiome changes drastically throughout life. You could have just as much difference between your microbiomes as a teenager and as an adult as between you and another person. And bacterial genetic diversity is huge across populations, ethnic groups, and diets. Shifts in diet can result in a very different composition of your gut bacteria within 24 hours.
This new understanding of what is passed on from generation to generation is incredible for us as organisms. Not only do we inherit traits like physical appearance and temperament, we inherit a relationship. The symbiosis our mother has with her bacterial cells is passed on to us. It’s as if we are given a puppy born of the trusty dog that our mother has had since the day she was born. And this puppy will develop and grow and change. If we treat it well it will grow strong and protect us just as we protect it. If we treat it poorly, and don’t feed it well or abuse it, it may turn around and bite us. And if we spoil it with too many treats and too little discipline it may become an overweight brat that can barely help us or help itself.
So as you celebrate thanksgiving this year, don’t forget to thank your mom for all she has done. You have more to thank her for than just those cute notes in your packed lunches, and the amazing turkey that she spent 10 hours on. You have your life to thank her for. And part of that life, is your symbiotic bacteria. Something you just can’t live without.