Plants Grow In Soil and Antibiotics Do, Too

This week’s stunning announcement that scientists have found a previously unknown antibiotic in soil is good news indeed. Not since 1987 have any new antibiotics been ‘discovered.’ And the news, described as a game-changer, comes at an opportune time. Disease-causing organisms have become resistant to most of the medicines available today.

Who knew soil produced antibiotics? I certainly didn’t. Yet, according to the researchers at Northeastern University in Boston (whose study was profiled in the journal Nature), it’s the source of nearly all of them.

As a gardener, I’m fairly familiar with soil. I know that it is full of microbes, and that many of them, such as bacteria, fungi, protozoa and nematodes play a key role in the health of my plants. They do this by working together with their larger co-inhabitants (worms and slugs), to condition and aerate the soil, convert organic matter into nutrients and provide plants with the ability to resist drought, pests and disease.

What I didn’t know is that microbes also compete with each other for dominance in the soil, forming mutually beneficial alliances to survive. They wage war using biological weapons. And those weapons are antibiotics.

Dr. William Schaffner, an infectious disease specialist at Vanderbilt University, put it this way,

“The way bacteria multiply, if there weren’t natural mechanisms to limit their growth, they would have covered the planet and eaten us all eons ago. “

Soil has provided fertile ground over the decades for many discoveries, including lifesaving antibiotics such as penicillin, (from a fungus) and vancomycin (from a bacteria.) Streptomycin and tetracycline were also discovered in this way as well as several powerful chemotherapy drugs for cancer.

The challenge for researchers, however, is that though soil is teeming with microbes, only one percent of them can be grown in the laboratory. The other 99 percent have remained uncultured; their potential benefits to medical science for the most part unknown.

This time around, researchers found a way of circumventing the problem, and in doing so, discovered a whole new antibiotic, teixobactin. According to lead scientist Professor Kim Lewis,

“Instead of trying to figure out the ideal conditions for each and every one of the millions of organisms out there in the environment, to allow them to grow in the lab, we simply grow them in their natural environment where they already have the conditions they need for growth. “

To trick the bacteria into thinking they were competing in their natural environment, the researchers created a “subterranean hotel,” essentially chambers surrounded by permeable membranes. Each bacterium was assigned to a sealed pod, or “room” and the whole device was buried in the soil.

The unique structure of the “hotel” allowed the bacterium access to nutrients and other growth factors, without allowing them to escape. As the microbes divided and formed new colonies in their native dirt, researchers were able to observe them. Once they were determined to be “domesticated,” the scientists scooped them up and placed them in petri dishes for further study. Teixobactin was discovered in this way.

According to Lewis, so far 25 new antibiotics have been found, in addition to teixobactin. The new antibiotic was the most promising candidate isolated from over 10,000 strains of bacteria, killing various types of staph and strep as well as anthrax and tuberculosis.

It’s enough to make you think twice next time you go digging in the soil.

Images via Shutterstock and Nature