Comparative Analysis of Anuran Amphibian Skin Microbiomes Across Inland and Coastal Wetlands
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Amphibians host a community of microbes on their skin that helps resist infectious disease via the dual influence of anti-pathogenic microbial species and emergent community dynamics. Many frogs rely on freshwater habitats, but salinization is rapidly increasing saltwater concentrations in wetlands around the globe, increasing the likelihood that frogs will come into contact with salt-contaminated habitats. Currently, we know little about how increased salt exposure will affect the symbiotic relationship between the skin microbes and frog hosts. To better understand how salt exposure in a natural context affects the frog skin microbiome, we use Hyla cinerea, a North American treefrog species that can inhabit brackish wetlands, to explore three questions. First, we determine the extent that microbial communities in the environment and on frog skin are similar across populations. Second, we assess the microbial species richness and relative abundance on frogs from habitats with different salinity levels to determine how salinity affects the microbiome. Third, we test whether the relative abundances of putatively pathogen-resistant bacterial species differ between frogs from inland and coastal environments. We found that the frog microbiome is more similar among frogs than to the microbial communities found in surface water and soil, but there is overlap between frog skin and the environmental samples. Skin microbial community richness did not differ among populations, but the relative abundances of microbes were different across populations and salinities. We found no differences in the relative abundances of the anti-fungal bacteria Janthinobacterium lividum, the genus Pseudomonas, and Serratia marcescens, suggesting that environmental exposure to saltwater has a limited influence on these putatively beneficial bacterial taxa.
KeywordsMicrobiome Anuran amphibian Frog Mutualism Skin Pathogen resistance Bacteria Secondary salinization
The authors would like to thank members of the K. McCoy and M. McCoy lab groups at East Carolina University for thoughtful insights in the development of this project. We thank Laila Kirkpatrick at Virginia Tech for laboratory assistance as well as Zach Herbert and the staff at the Dana-Farber Cancer Institute’s Molecular Biology Core Lab at Harvard University for Illumina sequencing. Finally, we thank two anonymous reviewers whose reviews helped improve this manuscript.
MA and MM conceived the study; MA and MM performed the field sampling; LB analyzed the samples; and MA, MM, and LB analyzed the data. MA, MM, and LB contributed to the writing of this manuscript.
Funding for this study was provided by the NSF grant DEB 1136640 awarded to Lisa Belden and the North Carolina Sea Grant (Project No. 2014-R/14-HCE-3) awarded to Michael W. McCoy and Molly A. Albecker.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflicts of interest.
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