Bacteria as a group exhibit the most extensive metabolic diversity because they utilize a vast array of nutritional strategies to survive in diverse and often extreme environments. Their metabolic processes include:

• Autotrophic Nutrition: Some bacteria synthesize their own food from inorganic substrates, categorized as either photosynthetic (using light) or chemosynthetic (oxidizing inorganic substances like nitrogen or sulfur).

• Heterotrophic Nutrition: The vast majority of bacteria are heterotrophs, obtaining energy from other organisms or dead organic matter through parasitic, saprophytic, or symbiotic relationships.