Antimicrobial resistance is becoming a greater threat, so researchers are looking everywhere for new substances. This week in mBio, a multinational team of researchers in Europe report the discovery of a new antifungal antibiotic named solanimycin. The compound was first found in a pathogenic bacterium that infects potatoes. It is made by a wide range of closely related plant-killing bacteria.
The researchers found that solanimycin inhibits a variety of fungi known to damage and infect agricultural crops. In laboratory tests, the substance also inhibited the growth of Candida albicans, a fungus that lives naturally in the body but can lead to potentially harmful infections. The results suggest that solanimycin and similar chemicals could be useful in both medical and agricultural settings.
The majority of therapeutic antibiotics used today are produced by soil microbes, particularly those belonging to the phylum Actinobacteria. According to microbiologist Rita Monson, Ph.D., of the University of Cambridge, the new finding suggests that plant-based microorganisms are worth further investigation, particularly as crops grow resistant to current treatments. She and Miguel Matilla, Ph.D., a molecular microbiologist, led the investigation at the Spanish Research Council’s Estación Experimental del Zaidn in Granada.
Monson said, “We need to look at a lot more of the microbial populations we have at our disposal.”
Solanimycin is produced by the pathogenic potato bacterium Dickeya solani, which was discovered more than 15 years ago. About ten years ago, scientists in molecular microbiologist George Salmond’s lab at the University of Cambridge started looking into the substance’s antibiotic potential.
According to Matilla, “These strains emerged quickly and are now widely distributed.”
The first antibiotic derived from the microbe is solanimycin. Scientists have found that D. solani makes the antibiotic oocydin A, which is very effective against a wide range of plant pathogens that are caused by fungi.
These earlier findings suggested that the bacterium might produce additional antibiotics with the potential to be antifungal, according to Matilla, who also analyzed the genome of the organism. That tip paid off: Matilla, Monson, Salmond, and their colleagues discovered that the bacterium continued to exhibit antifungal activity even after silencing the genes responsible for the production of oocydin A.
The compound solanimycin and the gene clusters in charge of the proteins that produce it were discovered as a result of that observation.
The scientists discovered that the bacterium produces the compound in response to cell density and uses it sparingly. The solanimycin gene cluster is also activated by an acidic pH environment, like the one found in potatoes. According to Monson, it almost seems like a clever protective mechanism.
The antifungal, according to Monson, “will work by killing fungal competitors, and the bacteria will benefit greatly from this.” But unless you’re inside a potato, you can’t turn it on.
Monson stated that in order to better understand the molecular makeup of solanimycin and how it functions, scientists have started working with chemists. She then added that she and Matilla hoped for more research on the substance using plant and animal models.
Our next steps will try to use this antibiotic antifungal for plant protection, according to Matilla. The research team thinks that this is a good sign that plant pathogens like D. solani could be made to make chemicals that could be used to treat diseases in both plants and people.
To find new antibiotics, Matilla said, “We have to be open to the exploration of everything that’s out there.”
