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Good to Eat, Wholesome to Digest

Bruce Rinker
Bruce Rinker

The American satirist Ambrose Bierce offered the following definition of “edible” in his 1911 book, The Devil’s Dictionary: “good to eat, and wholesome to digest, as a worm to a toad, a toad to a snake, a snake to a pig, a pig to a man, and a man to a worm.”  Gardeners often use this quote to promote composting; epicureans, good food; self-help guides, humility and positive thinking; medical experts, healthy lifestyles; and cynics, bankers and lawyers.  Bierce’s biting satire seems to extend well into the 21st century!

As a forest ecologist, I like the quote because it’s an engaging metaphor for nutrient cycling.  Now before you turn the page and back away from a stiff term like “nutrient cycling,” let’s give it another look by way of example.  Nitrogen inundates the air we breathe: in fact, 78% of our air consists of nitrogen – unless you’re the Mona Lisa as you hang at the Louvre inside a sealed bullet-proof case with 100% nitrogen gas to prevent your decay from oxygen.  Eight out of every 10 molecules of air is nitrogen!  Under ordinary conditions, however, the nitrogen in our air does not react with other elements.  We scientists call it a stable molecule.  Yet nitrogen compounds are found in all fertile soils, in all living things, and in many foodstuffs.  Importantly, it’s a key component of protein and DNA.  If nitrogen is so stable, how did it get inside us to become vital parts of life’s macromolecules?

The answer: bacteria.

More than 90% of all nitrogen fixation is effected by these little critters.  Some of them are free-living.  Others are associated with legumes, cereal grasses, and other plants.  Aside from commercial nitrogen-fixation processes, it’s a diminutive array of microorganisms that sustains us.

In the jargon of computer-speak, they are the linkerati.  In the parlance of ecologists, they are keystone organisms.  Analogous to the role of a keystone in an arch, they have a disproportionate effect on their environments relative to their abundance or total biomass.  As Pulitzer prize-winning scientist E.O. Wilson so aptly declared, it’s “the little things that run life.”  Yet we effortlessly call them “germs” … or we yawn and turn the page.

We all marvel at the venerable age of the world’s oldest living trees.  For example, bristlecone pines in the western United States are generally recognized as the oldest continuously standing trees (around 5000 years old).  In 2004, researchers in Sweden found a Norway spruce with a root system that has been growing for 9550 years!  But these astounding statistics don’t even compare to 3 billion years – the earliest undeniable form of life fossilized in rock – with continuous lines of descent from that distant past.  Those early forms of life were bacteria-like.  Today we call their living single-celled progeny “archaea” because they live in oxygen-free environments that mimic the conditions of the early Earth.  Imagine a family tree with 120 million generations!

Some of those archaeans and some modern bacteria hold a monopoly on nitrification.  Without them, ultimately, all other organisms – humans included – would be incapable of protein synthesis and DNA replication.  That’s a spectre too horrible to contemplate.

Folks in Indonesia have a popular saying: “Without bamboo, the land dies.”  Across the planet, we can say assuredly, in parallel fashion, “Without nutrient cycling, the world dies.”  Nitrogen fixation is just one example.  Many of these cycles are sustained by bacteria and their kin, the smallest and oldest living things on the planet.  Let’s stop calling them “germs” or “bugs” or other negative appellations.  They are cause célèbre for life itself.

Good to eat, wholesome to digest.  As we approach our fall harvests, and our palates savor the delectable gifts of the season, let’s not overlook our appreciation for all creatures, great and small.  Just a thimbleful of rich Roanoke soil can hold nearly a billion bacteria along with several miles of fungi, several hundred thousand protozoa, and several hundred nematode worms.  That’s a lot of labor on a Lilliputian scale!

In the 1500s, Leonardo Da Vinci proclaimed, “We know more about the movement of celestial bodies than about the soil underfoot.”  For much of the world, his proclamation still holds true today.  Remember: it’s the little things that run life.

H. Bruce Rinker, Ph.D.
Science Department Chairman
[email protected]

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