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Bacteria show promise in fending off global amphibian killer
May 23, 2007First in a petri dish and now on live salamanders, probiotic bacteria seem to repel a deadly fungus being blamed for worldwide amphibian deaths and even extinctions. Though the research is in its early stages, scientists are encouraged by results that could lead the way to helping threatened species like mountain yellow-legged frogs of the Sierra Nevada mountains of southern California.
The research, conducted by biology Professor Reid N. Harris at James Madison University, Harrisonburg, Va., and funded by the National Science Foundation, is being presented May 23, 2007 at the 107th General Meeting of the American Society for Microbiology (ASM) in Toronto.
Experiments have shown that Pedobacter cryoconitis, bacteria found naturally on the skin of red-backed salamanders, wards off the deadly chytridiomycosis fungus. In late 2004, Australian researchers cited chytridiomycosis as one of the main factors imperiling up to one third of the world's amphibian populations.
"The exciting aspect is that we identified at least one bacterium from the skin that in both the dish and on the salamander aids the healing process - one species of bacteria which you could tentatively view as a probiotic," says Harris.
Harris hatched the idea of using the bacteria to fight the skin fungus while researching another amphibian killer, a fungus that attacks their eggs and embryos. Research by other scientists indicated bacteria on some amphibians produced compounds that were active against the egg fungus.
"So we were starting to work on that and then it suddenly clicked that the emerging fungus killing adults was a chytrid fungus and that the skin bacteria producing antibiotics against the egg fungus could do the same against the chytrid fungus," says Harris.
Working with another scientist at Duke University, Harris was able to create the petri dish experiment, which clearly shows the skin bacteria fending off the fungus. Harris then secured funding from the National Science Foundation. He also has repeated the petri dish experiment on live salamanders.
With the help of postdoctoral assistant Antje Lauer and his students, Harris is continuing work to isolate the most effective antifungal bacteria and grow them in the lab. Of the two he has tested so far, one (Pedobacter cryoconitis) has speeded the recovery of infected animals while the other (Pseudomonas reactans) has tended to slow the process, at least on the salamanders.
"There will have to be careful testing," say Harris. "Just because on the Petri plate you find a species of bacteria that is anti-chytrid doesn't mean it's going to be anti-chytrid on the amphibian. So we're going to have to do some tests to make sure which ones are actually most affective on the organism. But we did find one."
Eventually, the research could lead to procedures for "vaccinating" endangered populations, Harris said. Other questions, such as whether bacteria from one species could be used to help another, also could be addressed with future research.
American Society for Microbiology
"The exciting aspect is that we identified at least one bacterium from the skin that in both the dish and on the salamander aids the healing process - one species of bacteria which you could tentatively view as a probiotic," says Harris.
Harris hatched the idea of using the bacteria to fight the skin fungus while researching another amphibian killer, a fungus that attacks their eggs and embryos. Research by other scientists indicated bacteria on some amphibians produced compounds that were active against the egg fungus.
"So we were starting to work on that and then it suddenly clicked that the emerging fungus killing adults was a chytrid fungus and that the skin bacteria producing antibiotics against the egg fungus could do the same against the chytrid fungus," says Harris.
Working with another scientist at Duke University, Harris was able to create the petri dish experiment, which clearly shows the skin bacteria fending off the fungus. Harris then secured funding from the National Science Foundation. He also has repeated the petri dish experiment on live salamanders.
With the help of postdoctoral assistant Antje Lauer and his students, Harris is continuing work to isolate the most effective antifungal bacteria and grow them in the lab. Of the two he has tested so far, one (Pedobacter cryoconitis) has speeded the recovery of infected animals while the other (Pseudomonas reactans) has tended to slow the process, at least on the salamanders.
"There will have to be careful testing," say Harris. "Just because on the Petri plate you find a species of bacteria that is anti-chytrid doesn't mean it's going to be anti-chytrid on the amphibian. So we're going to have to do some tests to make sure which ones are actually most affective on the organism. But we did find one."
Eventually, the research could lead to procedures for "vaccinating" endangered populations, Harris said. Other questions, such as whether bacteria from one species could be used to help another, also could be addressed with future research.
American Society for Microbiology
Amphibian Current Events and Amphibian News RSSSmithsonian scientists find the frog legs trade may facilitate spread of pathogens
Most countries throughout the world participate in the $40-million-per-year culinary trade of frog legs in some way, with 75 percent of frog legs consumed in France, Belgium and the United States.
Amphibians as environmental omen disputed
Amphibians, for years considered a leading indicator of environmental degradation, are not uniquely susceptible to pollution, according to a meta-analysis to be published in Ecology Letters.
Catching a killer one spore at a time
A workshop at the Smithsonian Tropical Research Institute in Panama has dramatically improved the ability of conservationists and regulatory agencies to monitor the spread of chytridiomycosis-one of the deadliest frog diseases on Earth.
The first gene-encoded amphibian toxin isolated
Researchers in China have discovered the first protein-based toxin in an amphibian -a 60 amino acid neurotoxin found in the skin of a Chinese tree frog. This finding may help shed more light into both the evolution of amphibians and the evolution of poison.
Pitt research suggests EPA pesticide exposure test too short, overlooks long term effects
The four-day testing period the U.S. Environmental Protection Agency (EPA) commonly uses to determine safe levels of pesticide exposure for humans and animals could fail to account for the toxins' long-term effects, University of Pittsburgh researchers report in the September edition of Environmental Toxicology and Chemistry.
Biologists rediscover endangered frog population
For the first time in nearly 50 years, a population of a nearly extinct frog has been rediscovered in the San Bernardino National Forest's San Jacinto Wilderness.
Mangrove-dependent animals globally threatened
More than 40 percent of a sample of amphibians, reptiles, mammals, and birds that are restricted to mangrove ecosystems are globally threatened with extinction, according to an assessment published in the July/August issue of BioScience.
UCLA scientists discover ultrasonic communication among frogs
UCLA scientists report for the first time on the only known frog species that can communicate using purely ultrasonic calls, whose frequencies are too high to be heard by humans.
Spring fishing season arrives... and with it, amphibian diseases
Waterdogs, they're called, these larvae of tiger salamanders used as live bait for freshwater fishing.
Amphibians may develop immunity to fatal fungus
Amphibian populations are declining worldwide, principally because of the spread of the fungal disease chytridiomycosis. Researchers know that some amphibian populations and species are innately more susceptible to the disease than others.
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