From Seed to Seed:
Plant Science for K-8 Educators

Plant-Microbe Relationships

Unfortunately, when most people think of microbes, or microorganisms, they think of "germs." And they look for ways to kill them. (Witness the popularity of antibacterial everything...hand soaps, cleansers, dish and laundry detergents.) And of course it's true that microbes-bacteria, fungi, viruses, and others-are the culprits in many deadly diseases and debilitating illnesses.

Gardeners may first associate microbes with the diseases affecting their plants. There are all sorts of wilt diseases; rust diseases; diseases that cause leaf spots, root rot, and mushy fruit; and diseases that seem to come from nowhere and kill our favorite plants. And, yes, most of these diseases are caused by microbes.

But it is not an overstatement to say that life could not go on without the presence of microbes. They are everywhere!

"Good" Microbes? The yeast used in bread- and beer-making, the "cultures" that make milk into yogurt and buttermilk, the penicillin you take for an infection, the "sour" in sourdough bread-even the bacteria in your digestive tract-these are all examples of "good" microbes.

Soil life. Less obvious, but just as important, are the microbes inhabiting the soil, and these too should be cherished and nurtured (at least most of them). Imagine for a moment if there were no "decomposers," the various insects, slugs, snails, earthworms-and microbes-inhabiting the soil, responsible for breaking down organic matter. We would soon be up to our eyeballs in piles of leaves, grass clippings, branches, and any other organic matter that falls to the ground! (Not to mention that our compost piles would get very big, very quickly.)

Then plants would begin to die off, since they depend on these decomposers to break down organic matter in the process releasing the nutrients within. Without the activity of these saprophytes (organisms that draw their nutrients from dead and decaying organic matter), carbon, nitrogen, sulfur, and other elements essential for plant growth would remain locked in large, insoluble organic molecules. By breaking down these large molecules, the microbes effectively "recycle" the nutrients so they can once again enter the biological cycles.

In effect, these "magicians" transform waste materials-kitchen scraps, grass clippings, manures-into valuable fertilizer!