Dr. Justin Sonnenburg

something like a parasite, but there are eukaryotes, there are fungi, there are also little viruses.

There are these bacteriophages that infect bacterial cells.

And those actually outnumber the bacteria like 10 to one.

So they're just everywhere there.

They kill bacteria.

And so there's these really interesting predator-prey interactions.

But overall, it's just this really dense, complex, dynamic ecosystem.

There have been some studies that have looked at whether there are microbes in the womb and microbes colonizing the fetus.

And there's some debate about this, but overall, it looks like that's not a big part of the equation of microbial colonization.

And so each time an infant is born, it's this new ecosystem.

It's like an island rising up out of the ocean that has no species on it.

And suddenly there's this like land rush for this open territory.

There also are a lot of different trajectories that developmental process can take because our microbiota is so malleable and so plastic.

And those trajectories can be affected by all sorts of factors in early life.

So an example is whether an infant is born by C-section or born vaginally.

Infants that are born by C-section actually have a gut microbiota that looks more like human skin

then it does like either the birth canal, the vagina microbiota, or the mother's stool microbiota.

Compound on top of that, whether you're breastfed or formula fed, whether your family has a pet or doesn't have a pet, whether you're exposed to antibiotics.

There are all these factors that really can change that developmental process and really change your microbial identity eventually in life.

We know from animal studies that depending upon the microbes that you get early in life, you can send the immune system or metabolism of an organism or other parts of their biology in totally different developmental trajectory.