The Importance of Prokaryotes

What roles do prokaryotes play in the living world?

You may remember the star actors in the last movie you saw, but have you ever stopped to consider whether there would be any film at all without the hundreds of workers who never appear on screen? Prokaryotes are just like those unseen workers. Prokaryotes are essential in maintaining every aspect of the ecological balance of the living world. In addition, some species have specific uses in human industry. Three roles played by prokaryotes in the environment are shown in Figure 20–13.

Decomposers Every living thing depends on a supply of raw materials for its survival. If these materials were not recovered when organisms died, life could not continue. By assisting in breaking down, or decomposing, dead organisms, prokaryotes supply raw materials and thus help to maintain equilibrium in the environment. Bacterial decomposers are also essential to industrial sewage treatment, helping to produce purified water and chemicals that can be used as fertilizers.

Producers Photosynthetic prokaryotes are among the most important producers on the planet. The tiny cyanobacterium Prochlorococcus is probably the most abundant photosynthetic organism in the world. This species alone may account for more than half of the primary production in the open ocean. Food chains everywhere are dependent upon prokaryotes as producers of food and biomass.

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FIGURE 20–13 Ecological Roles Played by Prokaryotes Prokaryotes play important roles in the environment as decomposers, producers, and nitrogen fixers. Apply Concepts What is the name of the type of ecological relationship found between Rhizobium bacteria and legume plants?

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