How do the bacteria that live in your your intestines help you?
1 Answer
They further digest food so that it can be absorbed and used.
Explanation:
Nature is lazy. Or perhaps another way to put it is - Nature doesn't like to reinvent the wheel.
The human body, for all its complexity and advancement, is made of remarkably few genes. From the wikipedia page regarding the Human Genome Project:
Findings[edit]
Key findings of the draft (2001) and complete (2004) genome sequences include:
There are approximately 20,500[32] genes in human beings, the same range as in mice.
The human genome has significantly more segmental duplications (nearly identical, repeated sections of DNA) than had been previously suspected.[33][34]
At the time when the draft sequence was published fewer than 7% of protein families appeared to be vertebrate specific.[35]
https://en.wikipedia.org/wiki/Human_Genome_Project
Scientists were shocked that so few genes were found - they anticipated millions. Where were the "missing" genes?
Turns out that the human body "outsources" a lot of functionality to friendly bacteria. One estimate is that of the 100 trillion cells in the human body, only 10% of them have human DNA. The rest belong to friendly bacteria.
One place where these bacteria live is in our digestive tract. Nutrients from the food we eat pass through the upper GI (Gastro-Intestinal) tract and down into the intestines where said nutrients are absorbed. But there's a lot of processing that needs to be done in the intestines to make those nutrients able to pass through the intestinal wall and be useful for the body. Enter the roll of bacteria.
Bacteria eat the nutrients and excrete material, other bacteria eat the excreted material (so yes, some bacteria eat other bacteria's poo), others eat other bacteria to keep their population in check... it's a wilderness in there. Anyway, as a result of the activity of bacteria, the nutrients are transformed into a useable form.
Quick note - friendly bacteria live all over our bodies. They are on our skin (to help keep invading bacteria out), our mouths, our lungs... places where scientists, even up to a few years ago, thought were sterile and where no bacteria lived, bacteria live there.
And as to why - the ability of certain bacteria to make these changes to nutrients has been in existence for millions of years. Rather than rework the process, the human body incorporated those bacteria into the digestive process.
And another quick example - the mitochondria that are the little engines within each and every cell - they are bacteria in their own right but have been harnessed to power human cells.
And another quick note - the microbiome of each person is unique. No two people have the same one!
