Does the bacteria consuming it not use the energy generated? How do we even process it? Like what does the bacteria give off or stomach do that our body converts into energy?
In: Biology
Food is most broken down by chemicals in your digestive system called enzymes. Bacteria help with the process but most of the energy in the food is directly absorbed into your blood plasma via your intestines.
The dry weight of all the bacteria in your body is about 100g. They can’t absorb a lot of food.
Most food is not broken down by bacteria, it’s broken down by acids, enzymes, and mechanical action. It’s mostly fiber that’s fermented in the guts, the sort of food that’s not as available to us in the short time food spends in us. Bacteria eat the complex carbohydrates and in turn some of them produce vitamins we need, as well as short-chain fatty acids. In essence they eat our waste and we eat their waste.
A better example would be the role of bacterial fermentation in ruminants like cows and sheep. They have enormous and complex stomachs and intestines designed to extract maximal nutrition from fibrous, difficult-to-digest vegetation. They first grind the plants with their teeth a little bit to break down fibers and some cell walls, then the mush is swallowed into their first stomach. Acids and enzymes in their saliva start the process of breaking down the feed. This food is then regurgitated in wads (cud) to be chewed further, at their leisure. When the cud is finally swallowed it moved to a second stomach called the Rumen, to be fermented by bacteria, protozoa and fungi, and that process takes a couple of days at least! The “bugs” eat the mush and produce sugars, fatty acids, vitamins, and so on. The cow extracts nutrition from that, and the “bugs” enjoy a safe environment with regular infusions of food. Those nutrients are extracted, along with water, in the third and fourth stomachs, and finally what’s left is expelled as waste.
The bacteria in your gut (mostly?) have different chemical pathways that they use to get energy from stuff. So they can break things down that your body itself can’t, and poop out things that your body *can* use. They use some energy for themselves in the process, but it’s still a net win for us.
Food is not broken down by bacteria in our gut.
The food we eat is digested in the stomach and small intestine, where most of the nutrients are also absorbed. Once the food reaches the colon, it’s basically just fiber and other minor stuff that you were not able to absorb. The bacteria in the colon then digest these leftovers, which actually produces some other things that are beneficial to us.
Your poop is basically fiber, water and bacteria from your gut.
There is a key difference here between food (macronutrients) and micronutrients.
Food is energy and the symbiotic organisms do get their share. But, they also can process raw materials into useful micronutrients. Iron, for example, is a vital micronutrient, but as a hunk of metal, it’s not very useful to the body. Once it is oxidized into ions, it is very useful. The beneficial bacteria in your gut do things like this to give you the micronutrients you need.
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