Was It Designed?

An Amazing Union in the Soil

▪ In the soil an amazing, cooperative union between certain plants and bacteria helps to make life possible.

Consider: Nitrogen is essential for plant growth and reproduction. But the gas has to be converted, or fixed, into compounds such as ammonia before vegetation can make use of it. Legumes solve this problem by working in close partnership with bacteria called rhizobia. Such a mutually beneficial union between unlike organisms is called symbiosis.

By means of a special chemical, the legume attracts the bacteria to its roots, which the bacteria then enter. Although the bacteria and the plant are members of two separate kingdoms, says Natural History magazine, they work together “to construct what is essentially a new organ: a fully operational nitrogen-fixing root nodule.” Inside the nodule, their new home and workshop, the bacteria get to work. Their main tool is a special enzyme​—a form of protein called nitrogenase—​which they use to fix nitrogen captured from air pockets in the soil.

“The planet’s entire supply of nitrogenase . . . could fit into a single large bucket,” says Natural History. So every molecule counts! But there is a problem. The enzyme is ruined by oxygen. The solution? The legume produces a special substance that snatches potentially harmful oxygen away.

A membrane around the nodule controls the exchange of ammonia, sugars, and other nutrients between microbe and plant. Like all plants, legumes eventually die. When they do, the ammonia stays in the soil. Thus, legumes have rightly been dubbed “green manure.”

What do you think? Could microbes and their plant partners “invent” such an amazing, incredibly complex life-support system, or do we have here yet another evidence of design?

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A root nodule

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Background: © Wally Eberhart/​Visuals Unlimited; inset: © Dr. Jack M. Bostrack/​Visuals Unlimited