What is the main role of bacteria in the digestive system?

Bacteria play a crucial role in the digestive system by aiding in the breakdown of complex carbohydrates and fibers that the human body cannot digest on its own. They help ferment these substances, producing short-chain fatty acids beneficial for gut health and overall metabolism. Additionally, these bacteria contribute to the synthesis of certain vitamins, such as vitamin K and some B vitamins. Overall, they support a balanced gut microbiome, which is essential for proper digestion and immune function.