The complex peptide mixture that makes ant venom a powerful shield

In addition to serving as biochemical weapons for offense and defense, the venoms produced by ants in the subfamily Formicinae also fulfill additional roles. For example, the ants use it to protect their nests from pathogens. It has long been assumed that the primary constituent of these venoms, formic acid, was responsible for these functions.

However, a team of researchers from Freie Universität Berlin and Martin Luther University Halle-Wittenberg has now shown that these venoms also contain a complex mixture of peptidic compounds and other bioactive substances.

The discovery of these substances opens up new possibilities in the field of medical research. It also has the potential to shed new light on immune defenses and how social insect communities deal with microbes. Researchers from Tübingen, Münster, Leipzig, Frankfurt am Main, and Cambridge (UK) were also involved in the study, the results of which were published in the journal Science Advances.

Ant venom more complex than previously thought

Since formic acid was first isolated from Formica ants back in the seventeenth century, the venom of these ants was considered to be rather simple in its composition. It was believed that formic acid served as the principal toxin, and although findings from earlier studies suggest the presence of peptidic compounds in the venoms, these observations were largely overlooked.

In our project, we investigated a decades-old publication that received little attention in its time. The paper mentioned that these venoms also contain peptidic compounds, We investigated the venoms of eight geographically distant species of carpenter ants and uncovered thirty-five peptides, or formicitoxins, belonging to two gene families. The specific make-up of the formicitoxins varied from species to species, but their presence was widespread. This means that carpenter ant venom is considerably more complex than previously assumed."

Timo Niedermeyer, Project Lead and Professor, Pharmaceutical Biology, Institute of Pharmacy, Freie Universität Berlin

A wide range of uses

The peptides that the researchers discovered likely contribute toward the hygiene of the ants' nest. The ants spread their venom onto the brood and the area surrounding the nest, leading the researchers to propose that the formicitoxins reinforce an external immune defense that lingers after the immediate antimicrobial effects of formic acid have lost their potency. "Some of the peptides demonstrate remarkable antifungal properties.

This is particularly interesting when we consider the threat that environmental microbes and pathogens pose to social communities such as ants, as well as the increased threat of microbial resistance for human well-being," emphasizes Dr. Simon Tragust, project lead at the Institute of Biology at Martin Luther University Halle-Wittenberg. "The Formicinae subfamily comprises over 3,700 species, meaning that there is enormous potential for the discovery of more bioactive substances."

The results confirm that carpenter ant venom performs a range of diverse functions. The ants use their venom not only for defense, but also to disinfect their surroundings, to acidify their gut for microbial selection, and to communicate with other ants.

Top international research

For their study, the researchers combined methods from the fields of biology, chemistry, and pharmacy. Using a proteotranscriptomic approach, they combined protein and RNA data taken from the venom and associated tissues to identify the individual peptides, as well as their genetic sequences.

They also made use of chemical analyses, performed bioactivity assays, and synthesized their own formicitoxins. The scientists gained further insight into the structure and evolutionary history of the individual venom components through biophysical experiments, genome analyses, and computer-assisted modeling.

Thanks to its interdisciplinary approach and the examination of venom from multiple ant colonies, this study represents one of the most comprehensive comparative analyses of ant venom carried out to date.