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MAY 15TH, 2017
The Microbiome: Where Germs Aren’t a Bad Thing
Mouse Guts
The Key to Unlocking the Microbiome Mystery
Welcome back to the human microbiome! In this post I’ll talk more about the history of the microbiome, and one other experiment conducted by
the National Institute of Health (NIH)—the one that pioneered the Human Microbiome Project itself.
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Although 20,000 human genes may sound like a lot, the truth is we have few genes compared to other living things on Earth. Russian scientist Ilya Metchnikov discovered microbes in 1882. Not long after scientists all over the world realized that we had good bacteria living within us. However, 125 years passed before the microbiome as a whole was conceptualized.
Every person has billions of microbes in their gut with each microbe containing 1,000,000 genes—10 times that of humans—despite the fact that microbes are 1/10 the size of a single cell in the human body.
“Whatever concerns health is of real public interest.”
Russian scientist
Ilya Metchnikov was the first to discover
‘good bacteria’
in 1882.
His work in macrophages and the immune system won him the Nobel Prize in 1908.
Clearly microbes are incredibly powerful, despite their microscopic size and covert existence. Not to mention our microbes know us better than anyone thanks to millions of years of co-evolution. However, we all have distinct microbes passed from mother to infant upon birth through the vaginal cavity. This special transmission has led to research concerning the susceptibility caesarian children may have to disease due to this lack of application of vaginal microbes upon birth. This idea was brought up in my first post, “Malawian Twins” with a microbe map by Rob Knight.
The map illuminates that the human microbiome consists of microbes residing in our nasal passages, oral cavities, gastrointestinal tract, and on our skin.
So how important is the health of our heroic microbes anyway?
The truth is they matter more than most think.
An experiment involving ‘germ-free’ mice brought this powerful intuition to light. This was the first experiment in the Human Microbiome Project dating all the way back to the mid 2000s.
The mice were raised in a contraption that vacuumed bacteria out of the air. This allowed them to grow up microbe-free. Microbes were extracted from adult human twins—one healthy twin and one obese twin—and inserted into individual mice. After being fed exactly the same kind of food, the mouse with unhealthy microbes from the obese twin would gorge themselves until the food ran out. On the other hand, the mouse injected with the healthy twin’s microbes would not overeat, and ultimately stayed fit and healthy.
You might be thinking that the one mouse got fat because he overeats. In a nutshell, it’s the messages the microbiome sends to the brain, which instructs the way the body uses (or stores) sugar. The obese mouse is experiencing a ‘disconnect’ where excess fat is being stored because the brain is receiving mixed signals from sickly microbes. A whole chain of events thwarts the mouse’s health—from the breakdown of fatty acids, slowed muscles regeneration, to poor calorie assortment.
For example, proper digestion was found to rely on microbe health in the study. Germ-free mice were given a common human microbiome that normally benefited the human colon. The mice became more energy efficient, improved prevention of unhealthy fat storage, and muscle growth.
This metabolism issue not only causes a breadth of health issues, but can be prevented with more research to determine the kind of microbes that create a healthy community partnered with an optimal caloric intake.​
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This proved that not only our diet, but also its effect on the microbes in our gut have a significant impact on our health, and even the development of disease.
Thanks to these lab rats, we learned that microbes:
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Mediate food digestion
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Strengthen our immune system
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Battle pathogens
This experiment paved the path to further ground-breaking microbiome research, including treatment for Kwashkior disease discussed in Post 1.
‘Mouse guts’ are the foundation of human microbiome research across the world—the very essence of the Human Microbiome Project. Without them, scientists couldn’t have determined the importance of the microbes in us.