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Wood ants produce a potent antimicrobial agent by applying formic acid on tree ‐ collected resin

View Article: PubMed Central - PubMed

ABSTRACT

Wood ants fight pathogens by incorporating tree resin with antimicrobial properties into their nests. They also produce large quantities of formic acid in their venom gland, which they readily spray to defend or disinfect their nest. Mixing chemicals to produce powerful antibiotics is common practice in human medicine, yet evidence for the use of such “defensive cocktails” by animals remains scant. Here, we test the hypothesis that wood ants enhance the antifungal activity of tree resin by treating it with formic acid. In a series of experiments, we document that (i) tree resin had much higher inhibitory activity against the common entomopathogenic fungus Metarhizium brunneum after having been in contact with ants, while no such effect was detected for other nest materials; (ii) wood ants applied significant amounts of endogenous formic and succinic acid on resin and other nest materials; and (iii) the application of synthetic formic acid greatly increased the antifungal activity of resin, but had no such effect when applied to inert glass material. Together, these results demonstrate that wood ants obtain an effective protection against a detrimental microorganism by mixing endogenous and plant‐acquired chemical defenses. In conclusion, the ability to synergistically combine antimicrobial substances of diverse origins is not restricted to humans and may play an important role in insect societies.

No MeSH data available.


Antifungal activity of pieces of resin, twigs, and stones that had been kept without or with ants, respectively. The boxplots show the median values of spore‐free areas around the tested items, as well as the upper and lower quartiles. The whiskers encompass 1.5 times the interquartile range. Outliers are indicated by circles
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ece32834-fig-0001: Antifungal activity of pieces of resin, twigs, and stones that had been kept without or with ants, respectively. The boxplots show the median values of spore‐free areas around the tested items, as well as the upper and lower quartiles. The whiskers encompass 1.5 times the interquartile range. Outliers are indicated by circles

Mentions: Pieces of resin that had been kept with wood ant workers showed a significantly higher inhibitory activity against M. brunneum than pieces of resin that had not been in contact with ants. In contrast, the presence of workers had no effect on the antifungal activity of twigs and stones (Figure 1; ANOVA, interaction between material and contact with workers: df = 2, F = 3.9, p = .022; Tukey's HSD post hoc tests: resin versus resin that had been in contact with workers: p < .0001; twigs versus twigs that had been in contact with workers: p = .99; stones versus stones that had been in contact with workers: p = .99). Overall, resin had higher antifungal activity than twigs or stones (Figure 1; ANOVA: df = 2, F = 57.6, p < .0001).


Wood ants produce a potent antimicrobial agent by applying formic acid on tree ‐ collected resin
Antifungal activity of pieces of resin, twigs, and stones that had been kept without or with ants, respectively. The boxplots show the median values of spore‐free areas around the tested items, as well as the upper and lower quartiles. The whiskers encompass 1.5 times the interquartile range. Outliers are indicated by circles
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383563&req=5

ece32834-fig-0001: Antifungal activity of pieces of resin, twigs, and stones that had been kept without or with ants, respectively. The boxplots show the median values of spore‐free areas around the tested items, as well as the upper and lower quartiles. The whiskers encompass 1.5 times the interquartile range. Outliers are indicated by circles
Mentions: Pieces of resin that had been kept with wood ant workers showed a significantly higher inhibitory activity against M. brunneum than pieces of resin that had not been in contact with ants. In contrast, the presence of workers had no effect on the antifungal activity of twigs and stones (Figure 1; ANOVA, interaction between material and contact with workers: df = 2, F = 3.9, p = .022; Tukey's HSD post hoc tests: resin versus resin that had been in contact with workers: p < .0001; twigs versus twigs that had been in contact with workers: p = .99; stones versus stones that had been in contact with workers: p = .99). Overall, resin had higher antifungal activity than twigs or stones (Figure 1; ANOVA: df = 2, F = 57.6, p < .0001).

View Article: PubMed Central - PubMed

ABSTRACT

Wood ants fight pathogens by incorporating tree resin with antimicrobial properties into their nests. They also produce large quantities of formic acid in their venom gland, which they readily spray to defend or disinfect their nest. Mixing chemicals to produce powerful antibiotics is common practice in human medicine, yet evidence for the use of such &ldquo;defensive cocktails&rdquo; by animals remains scant. Here, we test the hypothesis that wood ants enhance the antifungal activity of tree resin by treating it with formic acid. In a series of experiments, we document that (i) tree resin had much higher inhibitory activity against the common entomopathogenic fungus Metarhizium brunneum after having been in contact with ants, while no such effect was detected for other nest materials; (ii) wood ants applied significant amounts of endogenous formic and succinic acid on resin and other nest materials; and (iii) the application of synthetic formic acid greatly increased the antifungal activity of resin, but had no such effect when applied to inert glass material. Together, these results demonstrate that wood ants obtain an effective protection against a detrimental microorganism by mixing endogenous and plant&#8208;acquired chemical defenses. In conclusion, the ability to synergistically combine antimicrobial substances of diverse origins is not restricted to humans and may play an important role in insect societies.

No MeSH data available.