Skin microbes on frogs prevent morbidity and mortality caused by a lethal skin fungus

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.

Bacteria–bacteria interactions within the microbiota of the ancestral metazoan Hydra contribute to fungal resistance

“…A different example is the infectious disease chytridiomycosis, caused by the fungal pathogen Batrchochytrium dendrobatis, that is a major factor responsible for the worldwide decline of amphibian species (Skerratt et al, 2007). In this well-studied case, commensal bacteria have been shown to inhibit the growth of B. dendrobatis by the production of antifungal molecules like indole-3-carboxaldehyde or violacein (Brucker et al, 2008;Harris et al, 2009). Susceptibility to B. dendrobatis infection varies among amphibian species, and even within species some populations can coexist with B. dendrobatis whereas others decline to extinction.…”

Individual differences in boldness influence patterns of social interactions and the transmission of cuticular bacteria among group-mates

“…'behavioural competence'; [64]). Future experiments could also incorporate how the composition of resident cuticular microbial communities can combine with behavioural traits to drive the likelihood of bacterial colonization and transmission [65,66]. More specifically in regards to this system, it would be informative to identify the role that males play in social contact networks, including sexual interactions, and their influence on bacterial transmission.…”

Parasite and host assemblages: embracing the reality will improve our knowledge of parasite transmission and virulence

“…Cox 2001; Barton et al 2007;Cattadori et al 2007;Graham 2008), or at least the immune system mediates parasite competition (Bradley & Jackson 2008;Bush & Malenke 2008). Direct interactions may also exist, as in the case of bacteria that live on amphibian skin, excluding infections by pathogenic fungi through the production of fungicides (Harris et al 2009). The result is also an exclusion of these parasites and, consequently, an incomplete knowledge of the parasite's biology would lead to the erroneous view that there is no interaction between the parasites.…”