While we're busy fighting (and possibly losing) a war against superbugs, we might not realize that these organisms are constantly battling each other as well. Researchers from ETH Zurich have found a way to use that to our advantage, by making use of some of the chemical weapons they've developed against each other. In this case, that bacterial battleground is on the surface of thale cress leaves.

Antibiotic-resistant bacteria pose one of the greatest threats to humanity in the near future. Decades of overuse and overprescription have eroded away the effectiveness of these drugs, with more and more – including those considered our last line of defense – beginning to fail. A recent report suggested that if the problem isn't addressed, superbugs could be responsible for 10 million deaths a year by 2050.

Desperate to avoid that doomsday scenario, scientists have been frantically hunting down new antibiotic candidates, with promising leads so far found in honey, maple syrup, tobacco flowers, human breast milk, rattlesnake venom, yeast, ants, clay and platypus milk. On the synthetic side of things are developments like bacteria-killing polymers, gels, gene therapy or tweaks to existing drugs.

For the new study, the ETH Zurich team wanted to explore more natural avenues that may have been previously overlooked. In environments with dense microbial populations, where different bacteria species have to compete for space and resources, some of them develop antibiotic substances to kill off rivals. Soil habitats have previously been mined as a source of these kinds of drug candidates, but the researchers say that well has basically run dry.

Instead, the ETH team turned to thale cress leaves. A systematic search of these surfaces yielded 200 different bacterial strains, and through laboratory tests the researchers found over 700 antibiotic interactions between species.

One strain in particular caught the researchers' attention: an organism called Brevibacillus sp. Leaf 182. This bacterium was found to produce at least four antibiotic compounds, including one previously unknown chemical now known as macrobrevin. That cocktail allowed it to inhibit 100 of the 200 species found to share its leafy home.

That's a promising start, and although macrobrevin might not directly help us fight the superbugs we should be worried about, the study at least goes to show that there are new weapons still waiting to be found out there.

"We will now determine whether macrobrevin and other newly discovered substances are also effective against bacteria that cause diseases in humans," says Jörn Piel, co-lead author of the study. "This incredibly diverse ecosystem can most definitely still offer medicine many new leads. Our results confirm that it is worth expanding the search for antibiotics in nature."

The research was published in the journal Nature Microbiology.

Source: ETH Zurich

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