Amphibian Bacteria Fights Off Deadly Fungus, Study Says

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In a separate study in California, his team showed that northern populations of the mountain yellow-legged frog are able to persist despite chytrid infection, while southern populations drop to near-extinction levels when the disease arrives.

In the frog populations that co-exist with chytrid, there are more animals with at least one species of anti-chytrid bacteria living on their skin, Harris said.

The ability to isolate, grow, and apply the beneficial bacteria may make it possible to bolster the defenses of amphibians living in areas where the arrival of the disease is expected.

One option is capturing amphibians at ponds and bathing them with anti-fungal bacteria, Harris said.

"The concept would be to build a 'fire line' to stop the epidemic spread of the pathogen," he said.

Karen Lips, of Southern Illinois University, in Carbondale, has been studying the effects of chytrid disease on frog populations in Central America.

The work by Harris's team is an "important discovery," Lips said, "because it provides additional evidence that some species of amphibians have defenses that can successfully defeat the disease.

"Just as we have used microbes to break down chemical contaminants and fight agricultural pests," she said, "we might be able to figure out how to use this microbe to protect frogs from chytrid in captivity, and perhaps in the wild."

Bacteria on Board

Other research has shown that some frogs produce chemical compounds that are effective defenses against chytrid. But this ability seems rare.

Work by Harris and others has also shown that communities of beneficial bacteria living in a frog's skin secretions assist in fighting off many types of fungal infection.

Bacterial defenses may be particularly vital for amphibians that care for their eggs, Harris said.

In such species, parent frogs and salamanders coat the developing embryos in mucus that is rich in antibiotic compounds produced by resident bacteria.

Harris's team was studying how bacteria help protect amphibian eggs from a different fungal disease when they came across the anti-chytrid strains.

The researchers are now working to isolate additional and perhaps more effective varieties of protective bacteria, focusing on amphibian species that have survived in regions where others perished from chytrid.

But Harris also added a note of caution, saying that the fungal diseases explosive spread may have been triggered by outside factors.

(See related: "Frog, Lizard Extinctions Caused by Climate, Not Fungus, Study Suggests" [April 17, 2007].)

Amphibians may have become more susceptible to the disease because their protective bacteria may have been damaged by global warming or pesticide contamination, Harris said.

If so, Harris added, "applications of beneficial skin bacteria may not be a long-term solution until underlying factors are addressed."

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