Amphibian Bacteria Could Be Key to Saving Frogs from Extinction


The redback salamander is a natural host for Janthinobacterium lividum, a bacterium that could save frogs from a deadly epidemic. Image credit: WallTea/Flickr

Around the world, frogs are in trouble. Habitat loss is a major threat—as it is for many species—while pesticides and other chemicals cause deformities and disrupt reproduction.

But more serious, more deadly, than any of these things is a fungus called Batrachochytrium dendrobatidis that infects the skin and destroys entire communities of frogs. Now, a bacteria growing on the frogs themselves may bring salvation from this plague.
The irresponsible release of African clawed frogs is thought to be one cause of the Bd epidemic. Image credit: Wikimedia Commons
Batrachochytrium dendrobatidis (Bd) lives in symbiosis with some species of frogs—notably the African clawed frog. This frog, which responds radically to exposure to certain human hormones found in high-concentrations in pregnant women, was essential to early pregnancy tests. As technology advanced, however, the frogs were no longer needed and larger numbers were released into the wild.

These populations of invasive African clawed frogs are thought to be the culprits for the current Bd epidemic raging across North America.


The mountain yellow-legged frog is threatened by the spread of B. dendrobatidis, but the species may also hold the secret to the survival of frogs worldwide. Image credit: Wikimedia Commons

In many places, native frogs, like the mountain yellow-legged frog, have been extirpated from their traditional homes as a result of Bd infection. Worldwide, it is believed the fungus is responsible for the extinction of extirpation of more than 200 species. As scientists observed the spread of the fungus in California, however, they noticed something strange: Where some local populations were devastated, others dipped but survived.

The anomaly was a mystery, until researchers stumbled upon a bacteria, Janthinobacterium lividum, living on the skin of some frogs and other amphibians. Where this bacteria was present, frog populations were hurt by Bd outbreaks, but did not collapse.

Tests revealed that the concentrations of the bacteria were not as important as its presence before the introduction of Bd.

Reid Harris, a biologist at James Madison University who led the research, explained that these relationships are common in nature. He said:

Beneficial relationships like this are found in fluorescent pseudomonad species that protect plant roots from pathogenic fungi, for example. In sessile, [or immobile] marine organisms, epiphytic bacteria in sea lettuce prevent fouling

Now, the challenge is to maximize this natural resistance by using it to produce a safe and effective means of inoculating frog populations, before it's too late.

Read more about frogs:
Study of Frog Disease May Benefit Human Medicine
Trout Fishing Causing the Demise of...Frogs
Frog Bites Off More Than It Can Chew, Eats Entire Snake

Tags: Animals | Conservation | Endangered Species

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