section_path: Food sources/Microorganisms
section_name: Microorganisms
paragraph_text: Microorganisms
  
  Bacteria and other microorganisms also form the lower rungs of the food chain. They obtain their energy from photosynthesis or by breaking down dead organisms, waste or chemical compounds. Some form symbiotic relationships with other organisms to obtain their nutrients. Bacteria provide a source of food for protozoa, who in turn provide a source of food for other organisms such as small invertebrates. Other organisms that feed on bacteria include nematodes, fan worms, shellfish and a species of snail.
  
  In the marine environment, plankton (which includes bacteria, archaea, algae, protozoa and microscopic fungi) provide a crucial source of food to many small and large aquatic organisms.
  
  Without bacteria, life would scarcely exist because bacteria convert atmospheric nitrogen into nutritious ammonia. Ammonia is the precursor to proteins, nucleic acids, and most vitamins. Since the advent of industrial process for nitrogen fixation, the Haber-Bosch Process, the majority of ammonia in the world is human-made.