Gut by Giulia Enders

Author:Giulia Enders
Language: eng, eng
Format: epub, mobi
ISBN: 9781771641500
Publisher: Greystone Books
Published: 2015-03-26T16:00:00+00:00

Bacteria population density in the different regions of the gut.

One person might have stronger nerves than another because she has a better stock of vitamin B–producing bacteria. Another person might be able to deal easily with bit of bread mold eaten by mistake. Yet another might have a tendency to gain weight because the “chubby” bacteria in his gut feed him a bit too willingly. Science is just beginning to understand that each of us is an entire ecosystem. Microbiome research is still young, complete with wobbly milk teeth and short pants.

When scientists still knew very little about bacteria, they classified them as plants. This explains terms like gut flora, which is not scientifically accurate, but it is appropriately descriptive. A bit like plants, different bacteria have different characteristics concerning their habitat, nutrition, or level of toxicity. The scientifically correct terms are microbiota (which means “little life”) and microbiome, to refer to our collection of microbes and their genes.

In general, it is accurate to say that the number of bacteria is smaller in the upper sections of the digestive tract, while a very, very large number reside in the lower parts, such as the large intestine and the rectum. Some bacteria prefer the small intestine; others live exclusively in the colon. There are great fans of the appendix, well-behaved homebodies that stick to the mucus membrane, and rather cheekier chaps that nestle up close to the cells of our gut.

It is not always easy to get to know our gut microbes personally. They don’t like to be removed from their own world. When scientists try to grow them in the lab to observe them, they simply refuse to cooperate. Skin bacteria merrily gobble up the lab food and grow into little microbe mountains—gut bacteria don’t. More than half the bacteria that grow in our digestive tract are just too well adapted to living there to be able to survive outside the gut. Our gut is their world. It keeps them warm, moist, protected from oxygen, and supplied with pretasted food.

Only ten years ago, many scientists would probably have maintained that there is a stable stock of gut bacteria that is more or less common to every human being. For example, when they spread feces on a culture medium, they always found E. coli bacteria. It was as simple as that. Today, we have machines that can scan tiny amounts of feces molecule by molecule. This reveals the genetic remains of billions of bacteria. We now know that E. coli make up less than 1 percent of the population in the gut. Our gastrointestinal tract is home to more than a thousand different species of bacteria—plus minority populations of viruses and yeasts, as well as fungi and various other single-celled organisms.

You might think our immune system would pounce on this multitude of settlers. Defending the body from foreign invasions is high on the immune system’s to-do list. Sometimes it even wages war on tiny pollen grains that accidently get sucked into our nostrils.

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