Transcript

Overview

A digitally drawn comic featuring an orange cartoon zebrafish as the narrator.

Cover

How Gut Microbiomes Influence Social Behaviors

Illustrated by August Reitan

Written in collaboration with Judith Eisen

Cover Image: A zebrafish swims through a bubbly ocean full of cartoon molecules, viruses, fungi, and bacteria.

Page 1

Microbiomes!

Panel 1: An orange cartoon zebrafish addresses the reader, “Have you ever wondered how the bacteria in your gut are connected to the development of your brain? Probably not! But they impact everything!”

Panel 2: Gut Microbiomes! “Your gut microbiome is a collection of organisms in the gut including bacteria and even fungi as well as viruses.”

Page 2

The zebrafish is surrounded by bacteria, fungi, and viruses. It raises its eyebrow, “This sounds kind of scary. Aren’t bacteria bad for us? Some may be, but others are necessary for life as we know it. The bacteria we are talking about shaped how you developed into the human you are today!”

Page 3

Panel 1: “So why study this? Scientists discovered our gut microbiomes affect our social behaviors and how we act.”

Panel 2: Two people look at each other, preparing to have a conversation. Another image shows a diagram of a person’s head with a brain inside. “Let’s talk about the experiments done to test this hypothesis. To do that, let’s meet our trusty friend used in these experiments.”

Panel 3: “Zebrafish!” A small green fish with black stripes.

Page 4

Panel 1: “Zebrafish are important in this research because they are good test subjects.” The zebrafish narrator stands next to a diagram of the zebrafish lifecycle. At first the fish is mostly a small embryo wrapped around a large yolk sac. Over time, the embryo expands and unwraps while the yolk shrinks, eventually transitioning into a small underdeveloped fish, and finally a fully developed zebrafish.

Panel 2:

“Why?

• They reproduce fast.
• They are naturally social creatures.
• Young zebrafish are transparent, so scientists can see their internal organs without dissection.

Panel 3: “It is important to study social animals for this experiment. This way we can see how removing the microbiome affects them.” Two young zebrafish look at each other, mirroring the position of the two people in the previous page.

Panel 4: A young zebrafish brain. “In this experiment, the goal was to see if the microbiome is critical during the first week of life for normal brain development.”

Page 5

“Scientists sterilized the gut microbiomes of day-old zebrafish.” A one day old embryo curls around a yolk sac. A day fourteen zebrafish is fully fish shaped, but still smaller and more translucent than fully grown. A day thirty and older zebrafish is fully matured.

“They immediately gave the control group fish normal gut bacteria. These fish developed normally with gut microbiomes. The scientists waited a week to give a microbiome to the other fish. All fish were tested at two weeks old.”

Page 6

Panel 1: “The control fish, with a microbiome from the start, were social. But the fish who only had a microbiome for a week were not. These images show computer tracking of the fish’s movement. In this experiment these fish were placed in tanks beside each other, visible to one another.” A top-down view of two fish in separate tanks with a shared wall showing the fishes’ movements. Both fish swim back and forth near the shared wall. These are the “Controlled group of zebrafish (with a microbiome from the start). These fish went up to the glass to interact with each other more.”

Panel 2: Another two fish in two tanks with a shared wall. These fish swim in circles and random patterns around their tanks. “Zebrafish that only acquired a microbiome after their first week of life.”

Panel 3: “This result suggests that the microbiome is necessary during the first week of life for fish to become social.”

Page 7

Panel 1: “What causes this change in social development? The development of social skills require neurons in the ventral forebrain.”

Panel 2: “Without a microbiome, these neurons grow larger than normal. These larger neurons may form synapses with neurons located in inappropriate brain regions.” A series of neurons are connected to each other.

Panel 3: “Thus ventral forebrain neurons cannot carry out their normal functions.” A diagram of the brain.

Page 8

Panel 1: “Microglia are immune cells that reside in the brain and normally prune overgrown neurons.” A microglia, a large cell with lots of tendrils.

Panel 2: “Without the microbiome, there are fewer ventral forebrain microglia and they produced less of a protein required for pruning.” A microglia with an arrow pointing towards a brain.

Panel 3: “This suggests that the gut microbiome influences ventral forebrain neurons’ circuitry by regulating microglial activity.” Two diagrams: a human stomach and intestines, and a brain.

Page 9

Panel 1: “Humans also have gut microbiomes! And there is some evidence that atypical microbiomes correlate with neurodivergence.” A zebrafish and a human look at each other.

Panel 2: “However, it is difficult to study the effects of microbiomes in human development, making zebrafish a great organism to develop and test hypotheses that might lead to new therapeutic approaches.” Three zebrafish eggs.

Page 10

Some questions that still need to be answered:

“What molecules are created by gut bacteria? How do fish sense these molecules? How do these molecules influence microglia and neurons in the brain, changing social behavior?”

“Thank you for reading!”

Acknowledgements Page

Researchers:

• Joseph Bruckner
• Sarah Stendnitz
• Max Grice
• Dana Zaidan
• Michelle Massaquoi
• Johannes Larsch
• Alexandra Tallafuss
• Karen Guillemin
• Philip Washbourne
• Judith Eisen

Illustrator: August Reitan

Funders:

• Life Science Research Foundation
• National Institute of Mental Health
• National Institute of Child Health and Human Development
• National Institute of General Medical Sciences
• Oregon Developmental Biology Collaborators
• National Science Foundation
• John Simon Guggenheim Memorial Foundation
• Gordon and Betty Moore Foundation

Back Page

Microbiomes in our gut can affect how our brain develops. In this comic, learn about the experiments that show the connection between the gut microbiome and social development. And learn how atypical guy microbiomes might be connected to neurodivergence!

A cartoon zebrafish addresses the reader, “Let me take you through this journey involving guy microbiomes, zebrafish and you!”
This comic was created through the University of Oregon Science and Comics Initiative. December 2024.