Soil bioaugmentation with amphibian cutaneous bacteria protects amphibian hosts from infection by Batrachochytrium dendrobatidis

Amphibians worldwide are declining in part due to the disease chytridiomycosis caused by the cutaneous fungal pathogen Batrachochytrium dendrobatidis (Bd). While several experimental disease mitigation strategies are currently being tested, no proven implementable strategy exists to combat chytridiomycosis in the field. A plausible conservation strategy is the use of probiotic anti-Bd bacteria to combat chytridiomycosis (bioaugmentation). In this study, we examined the use of soil bioaugmentation in mitigation of chytridiomycosis in a laboratory experiment. Specifically, we sought to determine if the anti-Bd bacterial species Janthinobacterium lividum could be successfully introduced into natural soil, if the introduced bacteria could then be transmitted to the skin of the amphibian species Plethodon cinereus, and if the environmental transmission of J. lividum could reduce Bd infection on P. cinereus. We demonstrated that J. lividum can be successfully introduced into soil and can be environmentally transmitted to P. cinereus skin. We found that the environmental transmission of J. lividum inhibited colonization by Bd on the skin of P. cinereus five days post-Bd exposure. Soil bioaugmentation may be a feasible conservation strategy that could protect amphibians susceptible to chytridiomycosis from declines driven by the disease.

► The bacterial species Janthinobacterium lividum colonized natural soil after introduction.
► The introduced J. lividum was environmentally transmitted from soil to the skin of salamanders (Plethodon cinereus).
► Exposure to the pathogen Batrachochytrium dendrobatidis caused an increase in densities of J. lividum on P. cinereus skin.
► The presence of J. lividum in soil caused a significant reduction in prevalence of B. dendrobatidis on P. cinereus skin.