Just as you have a microbiome, the soil beneath your feet has one too.
And promising new research suggests it may have a surprising influence on food and human wellness.
The native flora here is dormant, in a deep winter slumber, rendering the landscape in monochromatic tans.
Jonathan Beer Photography
Almost nothing is growing outdoors.
That’s not so inside CIRES, where billions of microorganisms are thriving.
“You’re not supposed to see that,” Fierer quips.
Jonathan Beer Photography
Experts believe that these soil microbes could also have a big impact on the nutritional content of our food.
Plants need it to get to grow, but lack enzymes to break down nitrogen.
In legumes, for example, a soil bacteria calledrhizobiaattach to legume roots and perform this task.
Fungiin the soil help plant roots tap into nutrients, such as phosphorus and zinc, among others.
Plants require these minerals to generate chlorophyll, essential for photosynthesis, which produces glucose.
Some of that glucose gets secreted back into the soil, where it feeds the fungi.
Another action involves mycorrhizae, silk-like fungi that form vast spindly webs that can span several miles underground.
These filaments are like the internet of the soil microbiome facilitating communication between plants.
Soil bacteria and fungi also work in tandem to make minerals in the ground water-soluble.
Microbes also enable plants to produce antioxidants.
It’s an equitable trade because plantslike peopleneed these minerals to exist.
And a lot of farmland today has indeed been degraded.
These include cardiovascular disease, neurological disorders, anemia, increased risk of infection and depression.
And monoculture (cultivating the same crop year after year) damages the soil microbiome too.
A breeze that whips dirt into the air can deposit microbes onto plants' leaves.
When a plant is harvested, soil clings to its roots, chauffeuring microbes along for the ride.
The diversityand how relatively little is known about themis mind-boggling.
Fathoming the soil microbiome is like trying to chart every star in our galaxybillions and billions.
“We know they’re there,” Fierer says.
“We just don’t know what most of them do and how they interact with each other.”
What resembles a large white refrigerator sits in the center of the space.
It is an environmental growth chamber for cultivating plants, illuminated with blinding-white LEDs.
Fierer swings open its heavy door and a waft of humid, musty air escapes.
He slides out a clear bin containing 12 square plastic plates lined with seed germination paper.
On each sheet are eight wheat seeds in various stages of growth.
Some are a couple of inches tall, with sprouts and roots clambering along the paper’s surface.
And a few haven’t germinated at all.
Walsh mixed each sample with water, concocting a slurry to douse onto individual wheat seeds.
Benefits for Mood & Immunity
Dirt is where soil microbes live.
Once in our intestines, these microbes can fortify the human gut microbiome.
We’re also exposed to these bugs through soil itself.
The safest bet to do that is through consuming a varied diet of plantsand consuming plants frequently."
He points to a questionnaire given to volunteers in the American Gut Project.
“Now I have 4 tablespoons every night with dinner.”
vaccaewas among the gut microbes that could dispatch signals to the brain.
The two scientists conducted experiments in mice, injecting them withM.
vaccae, which under a microscope look like translucent yellow maggots.
“The bacteria activated a very specific subset of serotonin-containing neurons in the brain.
These neurons are known to govern emotions, especially depression,” Lowry tells me.
“People were taken aback by the idea that bacteria from the soil could have antidepressant-like effects.”
Lowry and Rook published their results in 2007, and a media deluge followed.
Here was tangible evidence that microbes from the soilwhen introduced into the body could potentially impact health.
Lowry and Rook continued experimenting, homing in on the biological mechanism responsible for the anti-depressive effects.
It turns out thatM.
vaccaetriggers a kind of emotional armor.
“It protects against inflammation in the brain in response to stress,” Lowry explains.
By 2016, he was able to demonstrate in animal studies thatM.
vaccaecould alleviate symptoms in a range of psychiatric disorders, such as stress-induced colitis and post-traumatic stress disorder.
Lab rats can be conditioned to react to fear using behavioral training.
Once a fear response is established, it can take weeks or even months to undo.
“But the rats that received the bacteria extinguished their fear within 24 hours,” Lowry says.
“It was mind-blowing to me.”
Lowry and his colleagues also wondered ifM.
“The bacteria completely prevented this cognitive impairment,” he says.
So I ask Lowry: Why aren’t we all takingM.
Granted, the results need to be replicated in humans.
But the short answer is that the strain ofM.
vaccaehe studied is not available as a supplement, at least not yet.
And it will take more research to tease all that out.
2.Harvest plants gently to keep the soil intact.
Try planting buckwheat, rye, clover or hairy vetch.
4.Apply compost.It helps return carbon, nitrogen and mineral nutrients to the soil microbiome and aerates the ground.
(Turning a small amount of soil to add new plants is fine.
It won’t disrupt the soil as deep down and broadly as tilling the whole garden would.)
So the focus now is on repairing that relationship.
“He wanted to know whether soil health translates into healthy food,” Taylor explains.
And the science appears to support this approach.
Plant-growth-promoting microorganisms, or PGPMs, have also come on the scene.
They’re part of a newer class of fertilizers, called biofertilizers.
Other firms are creating “biotic” fertilizers.
The same process occurs naturally in healthy soil, just much more slowly.
On my way out of the lab, Fierer shows me two large framed photos hanging on the wall.
Indeed, they found bacteria and fungi surviving in areas that had recently been covered in ice.
What he discovered was that soil microbes are terrestrial die-hards.
After all, they have been around for an estimated 4 billion years.
“Don’t worry about them being eradicated,” says Fierer.
Michael Behar is a Boulder, Colorado-based science and health writer.
This article was produced in collaboration with Successful Farming magazine.
This article originally appeared in EatingWell Magazine, June 2020.
