Amphibian Bacteria Fights Off Deadly Fungus, Study Says

Scott Norris
for National Geographic News
May 29, 2007

Bacteria that occur naturally on the skin of some salamanders can slow the progression of a deadly fungal disease responsible for mass die-offs of amphibians worldwide, a new study has found.

Because some amphibians do not carry the bacteria in sufficient amounts to battle the fungus, called chytrid, scientists took red-backed salamanders susceptible to the disease and bathed them in two separate types of bacteria.

Red-backed salamanders treated with laboratory-grown strains of the bacteria species Pedobacter cryoconitis, which had been isolated from disease-resistant individuals, were better able to fight off infection by the lethal fungus known as chytrid.

The finding strengthens the hope that biologists may be able to use the protective bacteria to inoculate some dwindling amphibian populations threatened by chytrid.

The chytrid epidemic has been particularly severe in portions of Central and South America and Australia.

The disease is ranked among the top perils facing amphibians—along with habitat destruction and climate change.

(See related: "Frog Extinctions Linked to Global Warming" [January 12, 2006].)

Reid Harris, of James Madison University in Harrisonburg, Virginia, delivered the new results last week at the annual meeting of the American Society for Microbiology in Toronto, Canada.

Harris's team had previously reported that eight different types of bacteria found in the skin secretions of two salamander species inhibited the growth of chytrid fungus in laboratory petri dishes.

The new work confirms that at least one bacteria species protects live amphibians, when administered at greater concentrations than may be present naturally.

Bacterial Armor

Many amphibian populations may naturally possess some anti-chytrid bacteria, Harris said, but not enough to keep the disease at bay.

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