Poison Dart Frogs: Unveiling the Secret of Skin Microbes and Toxic Alkaloids

Poison dart frogs, members of the Dendrobatidae family, have long fascinated scientists due to their vivid colors and potent toxins. These amphibians accumulate toxic alkaloids from their diet, which includes poisonous insects and other arthropods. Recent research reveals that these alkaloid chemicals not only deter predators but also increase the diversity of microbial species living on the frogs' skin. The study, published in Current Biology on December 4, sheds new light on the intricate relationship between poison dart frogs and their skin microbiome.

Researchers, led by biologist Stephanie Caty, set out to understand how these alkaloids influence the microbial community on the frogs' skin. The team collected bacteria and fungi samples from 11 species of dendrobatid frogs across various locations in Ecuador. They fed colonies of skin bacteria with ammonium and the alkaloid decahydroquinoline (DHQ), which were modified with heavy versions of nitrogen and carbon. Remarkably, some bacteria incorporated DHQ carbon atoms into their cells, suggesting they use alkaloid carbon to build new cell material.

"It does seem like [the bacteria are] using [the alkaloid carbon] to build up new cell material," – Caty

Caty's research indicates that the role of alkaloids extends beyond predator deterrence. The findings suggest that these chemicals also shape the microbiome on the frogs' skin, revealing a complex interaction between the frogs, their diet, and the microbes. Andrés Brunetti, a collaborator in the study, emphasized this growing complexity.

"So, now it’s not only the predator and the frog and the mites or the ants that they feed on that interact through alkaloids, but also the microbes," – Andrés Brunetti

The study sorted frogs into high, medium, and low alkaloid groups based on alkaloid levels in their skin. This classification highlighted a correlation between alkaloid concentration and microbial diversity. Such instances of bacteria consuming toxic alkaloids from nature are rare, making these findings particularly notable.

Poison dart frogs show increased resistance to infections, such as those caused by the chytrid fungus threatening amphibians worldwide. The study opens new avenues for research into how these frogs' unique microbiomes contribute to their resilience.