A multinational team of European researchers has discovered a new antifungal antibiotic called solanimycin. The compound, which was initially isolated from a pathogenic bacterium that infects potatoes, appears to be produced by a diverse range of plant-pathogenic bacteria.
The growing threat of antimicrobial resistance has prompted researchers to look for new compounds everywhere. This week in mBio, a multinational team of European researchers report the discovery of solanimycin, a new antifungal antibiotic. The compound, which was initially isolated from a pathogenic bacterium that infects potatoes, appears to be produced by a diverse range of plant pathogenic bacteria.
Solanimycin acts against a wide range of fungi known to infect and wreak havoc on agricultural crops, according to the researchers. In lab studies, the compound also acted against Candida albicans, a fungus that occurs naturally in the body but can cause dangerous infections. The results suggest that solanimycin, and related compounds, could be useful in both agricultural and clinical settings.
Our next steps will be to try to use this antibiotic antifungal for plant protection. We have to be open to exploring everything out there to find new antibiotics.Miguel Matilla
The majority of therapeutic antibiotics used today are produced by soil microbes, particularly those of the Actinobacteria phylum. According to microbiologist Rita Monson, Ph.D., of the University of Cambridge, the new discovery suggests that plant-based microorganisms are worth investigating further, especially as crops develop resistance to existing treatments. She co-led the research with molecular microbiologist Miguel Matilla, Ph.D., at the Estación Experimental del Zaidn of the Spanish Research Council in Granada.
“We need to look much more broadly across much more of the microbial populations that are available to us,” Monson said.
The pathogenic potato bacterium Dickeya solani, which produces solanimycin, was first identified more than 15 years ago. Researchers in the lab of molecular microbiologist George Salmond, Ph.D., at the University of Cambridge, began investigating its antibiotic potential about a decade ago.
“These strains emerged rapidly, and now they are widely distributed,” said Matilla.
Solanimycin is not the first antibiotic discovered from the microbe. Previous research discovered that D. solani produces an antibiotic called oocydin A, which is highly active against a variety of fungal plant pathogens.
Previous discoveries, as well as an analysis of the bacterium’s genome, suggested that it could synthesize additional antibiotics with antifungal properties, according to Matilla. Matilla, Monson, Salmond, and their colleagues discovered that when they silenced the genes responsible for the production of oocydin A, the bacterium retained antifungal activity.
That observation led to the identification of solanimycin and the identification of the gene clusters responsible for the proteins that make the compound.
The researchers found that the bacterium uses the compound sparingly, producing it in response to cell density. An acidic pH environment – as that present in a potato – also activates the solanimycin gene cluster. Monson said it almost looks like a clever protective mechanism.
“It’s an antifungal that we believe that will work by killing fungal competitors, and the bacteria benefit so much from this,” said Monson. “But you don’t turn it on unless you’re in a potato.”
Monson stated that the researchers have begun working with chemists to learn more about the molecular structure of solanimycin and better understand how it works. Then, she and Matilla stated that they hope to see the compound tested further in plant and animal models.
“Our next steps will be to try to use this antibiotic antifungal for plant protection,” Matilla said. The researchers see the discovery as an encouraging sign that plant pathogens, such as D. solani, can be coaxed into producing compounds that can be used to treat plant and human diseases.
“We have to be open to exploring everything out there to find new antibiotics,” Matilla said.