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"At first, it was thought the sting of all hymenopterans—from bees to ants—came predominantly from formic acid, which was first identified in the venom of wood ants back in 1670. Since then, toxinologists have come to appreciate the diversity of toxins in this insect order, especially when it comes to peptides, including honeybees’ inflammatory melittin to bullet ants’ excruciating poneratoxin. But until now, the idea has persisted that ants in the subfamily Formicinae, which includes carpenter ants, rely almost solely on formic acid.
When researchers compared the genomes of eight carpenter ant species, they spotted almost three dozen venom peptides—a veritable “arsenal” thus far unique to this subfamily of ants. Broadening their genetic search still wider, the team found these peptides—dubbed formicitoxins— in at least 20 other formicine genera.
These small proteins do all sorts of helpful things. “Some of the peptides demonstrate remarkable antifungal properties ,” ... which may explain why the ants spray their venom on their young. “While concentrated formic acid has strong immediate antimicrobial effects, the formicitoxins may serve as a persistent antifungal protective cloak after formic acid has lost its potency due to evaporation, dilution, or neutralization,” the team explained in the paper. Some formicitoxins were potent antimicrobials, which is especially intriguing given that carpenter ants are known to consume their own venom to modulate their gut microbiome ..."
"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. ... a team of researchers ... 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. ..."
From the abstract:
"Venom peptides are key to the evolutionary success of most venomous animals, including stinging ants. The stingless ant subfamily Formicinae is thought to rely solely on formic acid in their venoms, despite early, unsubstantiated hints of proteinaceous venom constituents.
Here, we show that carpenter ants, the largest formicine genus, produce a diverse venom peptide arsenal. Mass spectrometry and transcriptomics across eight geographically distant species uncovered 35 peptides, formicitoxins, belonging to two gene families.
Several formicitoxins display antifungal activity. Application to pupae delays fungal outgrowth, suggesting a role of the peptides in colony hygiene. Genome analyses revealed that formicitoxins are widespread but variable across the Formicinae. Our findings overturn the paradigm of formicine venoms as simple acid sprays and establish them as a source of bioactive peptides."
Ant Venom Serves Many Functions (original news release) "Groundbreaking discovery of antimicrobial peptides in ant venom has far-reaching implications"
Fig. 1 Fig. 1. Analysis of C. nicobarensis venom.
(A) C. nicobarensis major worker during acidopore grooming.
(B) Total ion current chromatogram of C. nicobarensis venom. Major peaks corresponding to venom peptides are labeled as formicitoxins FRTX1-Cnic1a (LDIKEIINKIISDIKEKIAKAL), FRTX2-Cnic1a (DIVSFLLELPKIIEEFFLKLINLFKLIF), and FRTX2-Cnic2a (NILSNIIDSIIHLLFEDFSRIFL). Signals corresponding to N-acylethanolamines (NAEs) are labeled as linoleoyl ethanolamide (LEA), oleoyl ethanolamide (OEA), linoleamidoethyl formate (LEA-f), and oleamidoethyl formate (OEA-f).
(C) Dissected venom apparatus of a C. nicobarensis major worker as used for extraction of venom and RNA.
(D) MALDI mass spectrum of C. nicobarensis venom showing molecular ions of FRTX2-Cnic1a and FRTX2-Cnic2a along with potassium adducts (+39 Da) and formyl esters (+28 Da). Inset: Magnified mass/charge ratio (m/z) range 3350 to 3550.
(E) Structures of LEA, OEA, LEA-f, and OEA-f.
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