Imagine a world where common infections become life-threatening. This isn’t science fiction. The overuse of antibiotics has led to a growing crisis: antibiotic resistance. Bacteria are evolving ways to evade these once-powerful drugs, leaving us vulnerable to infections.
But what if the answer wasn’t under our feet (in the soil), but on the backs of insects?
Recent research offers a glimmer of hope. Scientists have discovered a treasure trove of new antimicrobials — substances that kill microbes — produced by bacteria living on insects! This blog post dives into this exciting discovery. We’ll explore how these insect-derived antimicrobials offer a powerful new weapon in the fight against antibiotic resistance. You’ll learn about the insect microbiome, the surprising source of these promising antimicrobials, and why they might be even more effective than those traditionally found in soil microbes.
Where do antimicrobials come from?
A major source of antimicrobials is microbes. Bacteria and fungi produce antimicrobials in their everyday lives to fight against each other when they compete for food and/or space.
Most of the time, when researchers go looking for new antimicrobials, they focus their searching on antimicrobials produced by bacteria or fungi that live in the soil. As a result, most of the antimicrobials that have been discovered came from soil-dwelling bacteria. One species, in particular, is recognized for its ability to produce antimicrobials — Streptomyces — which I mentioned in another blog post for their ability to make geosmin (the smell of dirt). “Early screens for antibiotics found many exciting antibiotics from Streptomyces,” says first author Marc G. Chevrette. But Streptomyces also live on insects, some of which do not even live in a soil environment.
What are antimicrobials exactly?
The term “antimicrobials” includes all substances that inhibit or kill microbes: antibacterials, antifungals, antivirals, and antiparasitics. Some use “antibiotics” to mean all antimicrobials, but this is not entirely accurate. “All antibiotics are antimicrobials, but not all antimicrobials are antibiotics.”
Antimicrobial Resistance Is A Significant Problem
A significant problem that this study introduces is that “no new antimicrobial classes have been clinically approved in over three decades.” And with the rise of antibiotic resistance, there is real potential for running out of effective antibiotics. For some infections, this is already the case.
The Search For New Antimicrobials In The Insect Microbiome
To attempt to resolve this issue, scientists are searching for antimicrobials in new places. Dr. Cameron Currie’s lab at the University of Wisconsin–Madison, a group that focuses on insect and microbe interactions, led this study and is involved in a large collaboration called the Wisconsin Antimicrobial Drug Discovery and Development Center. Together with researchers from University of Wisconsin–Madison, Harvard University, University of Costa Rica, and University of São Paulo they asked the question, can we find undiscovered antimicrobials from microbes on insects (aka the insect microbiome)?
So, they isolated over 1000 Streptomyces species from insects in North and South America, including Southern pine beetles and fungus-growing ants. The Southern pine beetle is a pine tree pest that can actually end up killing these trees. Fungus-growing ants can be thought of as fungus farmers, using the fungus as a food-source. Think about it, these tiny creatures are farmers with fungus as their crops. Amazing!
The antimicrobials produced by the insect-associated Streptomyces species worked better against bacterial and fungal pathogens than those of the average soil Streptomyces species. One particular Streptomyces species, pictured below, produced a highly effective antifungal called cyphomycin. In the paper, the authors state that “significantly higher overall inhibitory activity of insect Streptomyces compared to soil strains suggests insects generally associate with strains with greater antimicrobial potential and thus represent a promising source for antimicrobial discovery.” How exciting is that?!
This is a huge deal because scientists keep rediscovering the same antimicrobials from soil microbes. But we need new antimicrobials in the pipeline because those currently in use are losing efficacy due to increasing antimicrobial resistance in bacteria and fungi.
You can follow the Currie lab and the first author Marc G. Chevrette on Twitter. You can also explore the Currie lab website here.
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