What do bacteria primarily break down?

Bacteria primarily break down fatty acids and carbohydrates, making this choice the most accurate. Bacteria play a crucial role in the decomposition of organic matter, where they metabolize these compounds to obtain energy and nutrients. They do so by using enzymes to catalyze the breakdown of carbohydrates, such as starches and sugars, and fatty acids, which are components of fats. This metabolic process not only provides energy for the bacteria but also contributes to the recycling of nutrients in ecosystems.

In various environments, such as in the human gut or in soil, bacteria facilitate the breakdown of complex carbohydrates into simpler sugars and fatty acids, which can be utilized by themselves and other organisms. This process is essential for maintaining ecological balance and supporting life forms that depend on decomposed organic materials for their nutrition. While the other options mention important biomolecules that bacteria can interact with, the primary substrates utilized by bacteria in terms of energy acquisition are indeed fatty acids and carbohydrates.