Probing for probiotic fungus-fighting frogs
Amphibians around the world are currently under assault by a chytrid fungus called Batrachochytrium dendrobatidis, or Bd. With over 200 species of animal currently threatened, researchers are trying to find a way to bolster them in an effort to preserve their ecosystems’ biodiversity. One approach as been a search for bacteria that could prevent or reverse the fungus’ effects, starting with Panamanian golden frogs.
The frogs are nearly extinct in the wild, but the bright yellow and black amphibians do remarkably well in captive breeding environments, where they are isolated from Bd. Using these captive frogs as a starting point, researchers are hoping to find a way to protect them for eventual release into their native habitats once again.
They started with a bacterium called Janthinobacterium lividum, which had been found on two species of salamanders and the Mountain Yellow-Legged frog. What’s more, it had been found to be transferable to new individual yellow-legged individuals and provide protection from Bd. But introducing the bacterium to the golden frogs didn’t stick. They didn’t gain protection from the fungus, and so the next idea was to try to find a similar bacterium that came from the golden frogs native Panama.
Five survivors and many more questions
After numerous surveys and variations, only five golden frogs seem to have demonstrated protection from Bd, although the team can’t be sure what to credit for that success. Were earlier doses of probiotic candidates too small to make a difference? Were they incompatible with the frogs’ environment? Were the doses large enough to upset the frogs’ immune responses?
It may be that the inconvenient and unfortunate answer lies with the delicate balancing act of a good probiotic. The number of variables in that micro-ecosystem is huge, and involves neighboring bacteria, the disposition of the host’s immune system, and the question of just how the target bacterium is supposed to help— it may be releasing an anti-fungal agent, or it might just be occupying a niche in the environment preventing the unwanted pathogen from setting up shop in the first place.
For the golden frogs, work is now centered around 200 animals at the Maryland Zoo, where they hope to find what helped the five Bd survivors and replicate it for others, eventually taking that treatment back to the jungle.
Source: Can Probiotic Bacteria Save An Endangered Frog? by Ed Yong, Not Exactly Rocket Science