Genome offers clues to amphibian-killing fungus

Javascript is currently disabled in your web browser. For full site functionality, it is necessary to enable Javascript. In order to enable it, please see these instructions. 12 hours ago by Krishna Ramanujan Harlequin frogs, such as this species (Atelopus glyphus), are highly susceptible to Bd, and many populations have become extinct. Credit: K.R. Zamudio

A fungus that has decimated amphibians globally is much older than previously thought, but may have recently spread through the global wildlife trade to new locations where amphibians have no immunity, reports a new study.

Previous research had suggested that a group of related strains of the fungus Batrachochytrium dendrobatidis (Bd) responsible for the current global pandemic, called the Global Panzootic Lineage (GPL), resulted from a recent lethal hybridization.

But now, an international team of researchers, including Cornell ecologist Kelly Zamudio, one of the project's principal investigators (PI), has sequenced the genomes of 29 strains of the Bd fungus worldwide.

The results are published in the May 6 issue of the Proceedings of the National Academy of Sciences.

The findings reveal that the GPL existed long before the current pandemic, possibly descending from an ancestor that originated 26,000 years ago.

"We found a lot more genetic variation than people knew about," said Zamudio, professor of ecology and evolutionary biology, of the sequenced Bd genomes. "It could lead us to a better understanding of what makes it kill. Once we know the genetic makeup of a pathogen, maybe we can understand what makes it such a powerful killer."

The fungus infects some 350 amphibian species by attacking and degrading their skin, often causing death. Amphibians began dying off at alarming rates in the 1980s, particularly in Australia and South America, and researchers identified Bd as the culprit in 1998.

In the study, a sample from Brazil showed the earliest known divergence from that common ancestor.

"Early on in the history [of Bd], the Brazil isolate took a different evolutionary path," said Zamudio.

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Genome offers clues to amphibian-killing fungus