Final answer:
The three major processes that gut microbes are involved in are fermentation, which produces short-chain fatty acids, nitrogen fixation important for soil bacteria and plant growth, and cellulose degradation, aiding in the breakdown of fiber.
Step-by-step explanation:
Gut microbes are heavily involved in a variety of processes that are vital to human health. The correct answer to the question about the 3 major processes that gut microbes are involved in would be option B) Fermentation, nitrogen fixation, cellulose degradation.
Fermentation
Fermentation is a process where gut bacteria break down indigestible carbohydrates which result in the production of valuable short-chain fatty acids (SCFAs) such as acetic, propionic, and butyric acids. These are absorbed by the body and used as a source of energy.
Nitrogen Fixation
In the context of the gut microbiome, nitrogen fixation is not a principal role. However, certain soil bacteria are able to convert atmospheric nitrogen into ammonia through nitrogen fixation, a process important for plant growth and soil health.
Cellulose Degradation
The cellulose degradation is particularly important in the guts of herbivores where cellulose from plant material must be broken down. Human gut bacteria also contribute to this process to a lesser extent, aiding in the breakdown of fiber that reaches the colon.
In summary, gut microbes contribute significantly to human health by their roles in fermentation, the breakdown of cellulose, and by contributing to broader ecological nitrogen processes, albeit less directly in the human gut.