A natural product made by bacteria in the genus Pseudomonas has been found to have antimicrobial properties. The substances, named keanumycins, have been shown in a new study to be effective against fungi that cause disease in both plants and humans.
The rise in antimicrobial resistance means there is an urgent need to find new ways to combat microbial pathogens. We often hear about antibiotic resistance, but fungal infections are also an increasing threat to human health – and not only for their zombification potential. Beyond that, fungal pathogens are a major cause of crop losses across hundreds of plant species.
“We have a crisis in anti-infectives,” explained study author Sebastian Götze, of the Leibniz Institute for Natural Product Research and Infection Biology, in a statement. “Many human-pathogenic fungi are now resistant to antimycotics – partly because they are used in large quantities in agricultural fields.”
The authors of the new study had been working with Pseudomonas bacteria for a while, as it was known that they were toxic to certain amoebae (Dictyostelium discoideum). The researchers have now been able to isolate one of the groups of natural products responsible for this toxicity.
These newly discovered lipopeptides are such efficient killers that only one name seemed appropriate: keanumycins, inspired by Keanu Reeves’ iconic portrayal of hitman John Wick.
Since amoebae and fungi share some characteristics, the researchers suspected that keanumycins might also be effective at killing fungi. This suspicion was confirmed when fluid containing keanumycin from cultured Pseudomonas bacteria – called supernatant – was able to combat gray mold rot on hydrangea leaves.
“Theoretically, the keanumycin-containing supernatant from Pseudomonas cultures could be used directly for plants,” said Götze. It’s also biodegradable, so has far better environmental credentials than chemical pesticides. This was all an encouraging start, which the authors intend to follow up with further research, but it doesn’t only stop at plants.
"In addition, we tested the isolated substance against various fungi that infect humans. We found that it strongly inhibits the pathogenic fungus Candida albicans, among others," Götze continued. Promisingly, keanumycin seems to work at low concentrations without being highly toxic to human cells.
C. albicans recently made it onto a list of “critical priority” fungal pathogens compiled by the World Health Organization. It’s the fungus responsible for thrush, a common infection that often affects the mouth, throat, or genitals. In some patients, particularly those with suppressed immune systems, C. albicans can cause a serious and sometimes fatal systemic infection.
Fungal infections cause an estimated 1.7 million deaths each year – it’s been referred to as “the silent crisis”. With few drugs that specifically target fungi available, keanumycin may be a good starting point for the development of new, much-needed treatments.
The study is published in the Journal of the American Chemical Society. A companion News and Views article is also published in Nature.