Me, Myself
& Microbes

— LOADING —

What is this?

Professor Elaine Hsiao heads the Hsiao Lab in the Department of Integrative Biology & Physiology at UCLA where she teaches the class “Me, Myself, and Microbes”. Her lab researches how microbes affect our brains and behavior. Learn more about the lab and research:

Me, Myself & Microbes — A short story about bugs, guts & poop

We have co-evolved with trillions of microorganisms comprised of bacteria,
bacteria
viruses
viruses, fungi, and other microbes.
fungi
inside

Their estimated populations are staggering, a whopping a hundred trillion
gut
bacteria live in our guts. Ten billion in our mouths
mouths
and another one trillion on our skin. The belly
skin
belly
button alone contains dozens of unique species. Microbes inhabits
exposed
every exposed body surface. Even the extremely acidic and harsh environment of the stomach.
stomach

With a surface area of about thirty two square meters,
the gastrointestinal tract is the largest interface between us and our
intestine
environment. It contains the highest number and diversity of the microbiome.
lumen
Collectively, these microbes would weigh a hefty two to six pounds,
up to twice the weight of an average adult human brain.
villi

There are many pathways for microbes to impact brain and behavior.
One mechanism is by signalling to endocrine cells
endocrine
in the gut lining to produce neurotransmitters and neuropeptides.
These could enter the blood stream or signal to neurons that reach
neurons
the brain. Another way is by interacting with the intestine's immense
arsenal of immune cells. They constantly survey the
immune
environment and communicate with the nervous system.

Individual microbes themselves can also produce neuroactive molecules.
If these molecules manage to be absorbed through the gut lining and
pass into the bloodstream they could eventually affect the brain as well.
dna
Major changes in the numbers and types of microbes that inhabit us are
bacterium
phage
linked to many diseases and disorders including neurological conditions
like Parkinson's disease, autism, and major depression.

We're not merely hosts to these microbial inhabitants. In fact, some
of what makes a microbe a microbe is now directly integrated into our
own genetic makeup. It's estimated that viruses have cut their DNA
eight
and pasted it into our own so much that eight percent
of our human genomes are derived from viruses.

Sensory neurons that connect the gut to the brain are of great interest,
like the vagus nerve, which serves as a super highway between the small
vagus
intestine and the brain stem. The hope is that expanding our knowledge of how
gut
brain
we interact with our microbiome could one day
space
inspire new microbe based treatments for disease.
theend

The End