Animals in My Dirt! Soil Bacteria Keep Things Healthy


Animals in My Dirt!
  • Posted June 1, 2012

Did you know that just one handful of soil contains more “animals” than all the people on earth? 

Granted, these are little critters, but animals none the less. We are talking tiny bacteria, fungi, micro-algae, protozoa and a few bigger guys – nematodes, mites and earthworms. The most diverse society we have on planet Earth is right under our feet. This is not a boring, casual group like a book club.  Far from it! It is a rowdy collection of interdependent characters, caught up in life and death struggles that can be both tragic and heartening. Plant roots and seeds take part in the drama as secondary players.

We are talking animal life at the ground level!  It all starts with organic matter - plain old leaves for example, just like those on your lawn that you did not get around to raking last fall. Bacteria and fungi consume this organic matter and are in turn, voraciously devoured by nematodes, mites and earthworms. “That’s not really so exciting”, you say.  But knowing more about these individuals without doubt is. Our very existence depends on these little characters. Think soil, grass, beef, hamburger…dinner!

Let’s talk bacteria. I have to confess right now that bacteria are my hands down, fingernail dirty favorites. They are very tiny, one-celled organisms – generally 4/100,000 of an inch wide (1 millionth of a meter) and somewhat longer in length. What bacteria lack in size, they make up in numbers. A teaspoon of productive soil generally contains between 100 million and 1 billion bacteria. To compare, that is as much mass as two cows per acre of pasture. Moo!

Bacteria fall into four families, and sadly, some could be said to be dysfunctional. Most are in the first group known as decomposers, and they are not afraid to get dirty! Some can actually wipe out pesticides and pollutants in soil, and they keep on keeping on, and passing it to others. And you are just not going to believe this, but in 1940 there was a bacterium from this family that won a Nobel Prize! He did have some help from Selman Waksman who made it known that the bacterium was making antibiotics on the side. A second family of bacteria forms partnerships with plants - the original suck-ups!  The third family of bacteria is pathogens. A real shady bunch that could give the Mafia tips. The fourth and last families are called lithotrophs which actually break down stone into grains of sand. I can just see tiny little ladies with sledgehammers!  

My favorite bacterium star player at the moment is Mycobacterium vaccae, and this little guy holds the truth why more people should play in the dirt. UK scientists have discovered that Mycobacterium vaccae bacteria, found in nearly every soil, may affect the brain in a way similar to antidepressants. It activates brain cells to produce the brain chemical serotonin. Perhaps it is tied to that first deep breath you take that smells of warm, fresh earth filled with tiny animals……. After a long cold winter!

Sue Vargas
About the Author

Sue Vargas is a self-confessed plant freak, Advanced Master Gardener since 1993 and takes photos at MasterTag – a horticultural printing company.


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Animals in My Dirt!