Addition of antifungal skin bacteria to salamanders ameliorates the effects of chytridiomycosis

Abstract

Chytridiomycosis, caused by the skin fungus Batrachochytrium dendrobatidis (Bd), has caused population declines of many amphibians in remote protected habitats. Progress has been made in understanding the pathogen's life cycle, documenting its devastating effects on individual amphibians and on populations, and understanding how and why disease outbreaks occur. No research has directly addressed the critical question of how to prevent declines and extinctions caused by outbreaks of the disease. We have identified a number of bacterial species of amphibian skin that inhibit Bd in vitro. Here, we demonstrate that a species of anti-Bd skin bacteria can be successfully added to skins of salamanders Plethodon cinereus, and that addition of this bacterium reduced the severity of a disease symptom in experimentally infected individuals. This is the first demonstration that manipulating the natural skin microbiota of an amphibian species can alter the pathogen's negative effects on infected amphibians and appears to be the first demonstration that an epibiotic manipulation of any wildlife species can lessen the effects of an emerging infectious disease. It suggests that probiotic or bio-augmentation manipulations of cutaneous microbiota could have the potential to reduce susceptibility of amphibians to the disease in nature. This is the first approach suggested that could slow or halt epidemic outbreaks and allow successful reintroductions of amphibian species that have become locally or globally extinct in the wild. Our results also suggest a mechanism for the association of climate change and the likelihood of chytridiomycosis outbreaks via the effects of the former on antifungal bacterial communities.