1. ¹Department of Biology, James Madison University, MSC 7801, Harrisonburg, VA, USA
2. ²Department of Microbiology and Immunology, Vanderbilt University, Nashville, TN, USA
3. ³Department of Biological Sciences, Virginia Tech, MC 0406, Blacksburg, VA, USA
4. ⁴Department of Chemistry and Biochemistry, James Madison University, MSC 4501, Harrisonburg, VA, USA
5. ⁵Zoological Institute, University of Zurich, Zurich, Switzerland
6. ⁶Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, USA
7. ⁷Department of Biology, San Francisco State University, San Francisco, CA, USA

Correspondence: RN Harris, Department of Biology, James Madison University, MSC 7801, Harrisonburg, VA 22807, USA. E-mail: harrisRN@jmu.edu

Received 27 January 2009; Revised 23 February 2009; Accepted 23 February 2009; Published online 26 March 2009.

Abstract

Emerging infectious diseases threaten human and wildlife populations. Altered ecological interactions between mutualistic microbes and hosts can result in disease, but an understanding of interactions between host, microbes and disease-causing organisms may lead to management strategies to affect disease outcomes. Many amphibian species in relatively pristine habitats are experiencing dramatic population declines and extinctions due to the skin disease chytridiomycosis, which is caused by the chytrid fungus Batrachochytrium dendrobatidis. Using a randomized, replicated experiment, we show that adding an antifungal bacterial species, Janthinobacterium lividum, found on several species of amphibians to the skins of the frog Rana muscosa prevented morbidity and mortality caused by the pathogen. The bacterial species produces the anti-chytrid metabolite violacein, which was found in much higher concentrations on frog skins in the treatments where J. lividum was added. Our results show that cutaneous microbes are a part of amphibians' innate immune system, the microbial community structure on frog skins is a determinant of disease outcome and altering microbial interactions on frog skins can prevent a lethal disease outcome. A bioaugmentation strategy may be an effective management tool to control chytridiomycosis in amphibian survival assurance colonies and in nature.