Composition of symbiotic bacteria predicts survival in Panamanian golden frogs infected with a lethal fungus

Abstract

Symbiotic microbes can dramatically impact host health and fitness, and recent research in a diversity of systems suggests that different symbiont community structures may result in distinct outcomes for the host. In amphibians, some symbiotic skin bacteria produce metabolites that inhibit the growth of Batrachochytrium dendrobatidis (Bd), a cutaneous fungal pathogen that has caused many amphibian population declines and extinctions. Treatment with beneficial bacteria (probiotics) prevents Bd infection in some amphibian species and creates optimism for conservation of species that are highly susceptible to chytridiomycosis, the disease caused by Bd. In a laboratory experiment, we used Bd-inhibitory bacteria from Bd-tolerant Panamanian amphibians in a probiotic development trial with Panamanian golden frogs, Atelopus zeteki, a species currently surviving only in captive assurance colonies. Approximately 30% of infected golden frogs survived Bd exposure by either clearing infection or maintaining low Bd loads, but this was not associated with probiotic treatment. Survival was instead related to initial composition of the skin bacterial community and metabolites present on the skin. These results suggest a strong link between the structure of these symbiotic microbial communities and amphibian host health in the face of Bd exposure and also suggest a new approach for developing amphibian probiotics.

Short-Term Exposure to Coal Combustion Waste Has Little Impact on the Skin Microbiome of Adult Spring Peepers (Pseudacris crucifer)

“…In amphibians, several studies that have tried to treat adult amphibians with single or mixed probiotics have failed to see establishment of the bacteria, presumably due to competition with the resident microbes and/or host filtering (56)(57)(58). The same is true in human studies, although treatments with more complex mixtures of probiotics (e.g., fecal transplants) are often more successful (55).…”

The Influence of Brazilian Biodiversity on Searching for Human Use Pharmaceuticals

“…This paper should be read in conjunction with two others that show how the Panamanian frogs which had experienced a lethal fungal infection, have now overcome the infection via commensal microbes. 64,65 What was not mentioned however, is that these vertebrates contain toxins that almost certainly are adsorbed from their diet of specific ants.…”

Interactions between amphibian skin sloughing and a cutaneous fungal disease: infection progression, immune defence, and phylogenetic patterns

“…Given the potential importance of symbiotic cutaneous bacteria in innate immune defence against Bd infection (Harris et al 2009) Understanding that these species likely slough infrequently may help pinpoint when to best bioaugment their skin with beneficial anti-Bd bacteria (Becker et al 2011, Becker et al 2015, as addition of the bacteria immediately after sloughing may allow for colonisation when resident bacterial populations are low ).…”

“…Sloughing may also benefit the pathogen by revealing newly keratinised epidermis free of cutaneous symbiotic bacteria. It has been demonstrated that some symbiotic microbes on the skin of amphibians can prevent morbidity associated with Bd infection (Harris et al 2009;Becker & Harris 2010;Becker et al 2015), thus, sloughing may actually increase susceptibility of the epidermis to invading pathogens.…”

“…While some amphibian species are considered generally very susceptible to mortality from chytridiomycosis, such as Atelopus zeteki (and likely many other species of this genus) in Central and South America (La Marca et al 2005;Bustamonte et al 2010;Becker et al 2015;Ellison et al 2015), Rana muscosa and Rana sierrae in North America Rosenblum et al 2012), and Corroboree frog species (Pseudophryne corroboree and P. pengilleyi) in Australia Brannelly et al 2015), others appear to be resistant to infection, given they can reduce or eliminate Bd infection loads. There is little definitive evidence of species demonstrating widespread resistance to chytridiomycosis, but some species appear to demonstrate greater resistance than most, including the notorious invader Lithobates catesbeianus (Gervasi et al 2013;Eskew et al 2015), and threatened species in the genus Leiopelma (Bishop et al 2009;), amongst others (Woodhams et al 2007a;Gahl et al 2012;Searle et al 2011b).…”