In an effort to discover new kinds of antibiotics, researchers have identified new compounds from a chemical arms race in the environmental realm of ants and fungi. New work that utilizes mass spectrometry techniques is published today in Nature Communications and comes from a team of UK researchers at the University of East Anglia and the John Innes Centre.
Leafcutter ants collect leaves to cultivate a particular species of fungus, which serves as their staple food supply. However, the ants share an ecological adversary, another fungus known as Escovopsis, which can parasitize the ants’ fungus supply and lead to colony collapse. As it turns out, the leafcutters and the Escovopsis each have developed various chemical weapons against the other.
“Leafcutter ants are superb farmers. They patrol their gardens, remove foreign fungi and use antibiotic-producing bacteria on their bodies to kill off parasites—effectively using them as weedkillers. But the ways in which Escovopsis succeeds in getting through their defenses are not well understood,” said senior study co-author Matt Hutchings.
The team infected the samples of the ants’ fungal food supply with Escovopsis. Extracts taken from culture plates were then chemically profiled using ultra performance liquid chromatography coupled with high-resolution mass spectrometry (UPLC-HRMS). As a result, the team identified two overproduced compounds resulting from the infection.
The compounds, Melinacidin IV and shearinine D, had been shown to kill the symbiotic bacteria—known as Pseudonocardia—that live on the body of the leafcutter ants. Pseudonocardia are known to produce antifungal metabolites that protect the leafcutter food supply. In addition, shearinine D also influenced ant behavior, causing zombie-like effects and, ultimately, death.
The team believes that examples of these ecological observations and natural compounds can provide useful insight in the development of pharmaceuticals.
"This work highlights the key role that natural products play in the pest-control dynamics of farming ant colonies and is invaluable in aiding our search for new antibiotics from this unique battlefield where, in the long run, no party can permanently win. This may help us in future studies to address the antimicrobial resistance (AMR) crisis in human medicine." said senior co-author Barrie Wilkinson.
Image: The leafcutter ant shares a mutualistic relationship with Pseudonocardia bacteria. Image courtesy of the University of East Anglia.