New Antibiotic Compounds Discovered in Potatoes


In James Gunn’s 2006 sci-fi horror Slither, an alien encounters Earth and uses its parasitic behavior to infect the citizens of Wheelsy, South Carolina. The entity moves like a fungal infection, oozing over anything it touches and consuming what it finds. Fungi are about the strangest thing we have on our planet, some fungi work together, others seem to have complex communication systems and some of them make a living by infecting plants and animals including humans.

In fact, mushrooms are living on you right now. Most of the time this relationship is in balance and we don’t have a problem, but sometimes fungi grow out of control and cause infections that can lead to serious problems if left untreated. Each of us is waging our own personal war against an army of fungi and other microbes every moment of our lives. And the same goes for potatoes.

We don’t have much in common with these tasty tubers, but we do, and it’s enough that a team of scientists from the University of Cambridge are searching for potatoes in hopes of finding new antibiotics to combat the alien fungal plague. Recently, they managed to isolate a compound that appears to be effective against a variety of fungi. The results were published in the journal mBio.

Fifteen years ago, scientists discovered a new bacterium they named Dickeya solani that lives happily in potatoes. When it reproduces out of control, it is responsible for a number of destructive diseases, including blackleg and soft rot. Because we so often grow plants like potatoes in monoculture, plant-infesting pathogens have easy prey and can quickly spread among a population of similar plants in close proximity. Of course, many different pathogens will try to take advantage of the same organism, and they are all competing for the potato’s precious territory. So while the potato fights the bacteria, the bacteria also fight the fungi.

For this reason, D. solani has developed a defense against fungal invaders on its tattered lawn. In fact, this isn’t the first time this particular bacterium has offered a new antibiotic. Previous research identified a compound called oocydin A that is effective against fungal pathogens. This piqued the scientists’ interest in the bacteria, so they studied their genome. What they found in its DNA suggested it was able to produce additional antibiotic compounds. In later laboratory experiments, scientists turned off the bacteria’s ability to produce oocydin A, but the bacteria still fought fungi. With that, the hunt for whatever it was hiding in its back pocket began.

So researchers found a second compound called solanimycin that was highly effective at killing fungi. In the laboratory, the researchers confirmed that the compound is active against a wide range of fungi found in agricultural crops. In addition, it is also effective against Candida albicans, a type of yeast common in the human body that can cause more serious infections if it gets out of control. Interestingly, D. solani seems to be picky about when it produces solanimycin. It studies cell density and the acidity of the environment to know when to release the compound, and it turns out that the conditions inside a potato are just right to activate its production.

Solanimycin offers a new weapon in our antifungal arsenal, and while its medicinal uses show promise, it could really shine when it comes to protecting plants. Plant-infecting pathogens are a significant threat to global food security. So much so that, according to the authors, about 40% of annual crop losses are due to plant pathogens. Finding ways to effectively control them could dramatically increase crop yields without requiring more land.

Today, most of the antibiotics we use come from soil bacteria and that has largely remained the focus. The discovery of two different antibiotic compounds cooked in the fleshy interior of a potato points to an untapped microbial realm to look at.

Baked potatoes, mashed potatoes, french fries and now antibiotics. Is there anything potatoes can’t do?


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