Abstract
Fluctuating environments can modulate host–pathogen interactions by providing a temporary advantage to one of the interacting organisms. However, we know very little about how environmental conditions facilitate beneficial interactions between hosts and their microbial communities, resulting in individual persistence with a particular pathogen. Here, we experimentally infected Eleutherodactylus coqui frogs with the fungal pathogen Batrachochytrium dendrobatidis (Bd) under environmental conditions known to confer the survival advantage to the host during the warm-wet season, or alternatively to the pathogen during the cool-dry season. We used 16S rRNA amplicon sequencing to quantify changes in bacterial richness and phylogenetic diversity, and identified operational taxonomic units (OTUs) that became overrepresented or suppressed as a consequence of Bd infection. During the warm-wet season, frogs limited Bd infections, recruited putatively beneficial bacteria and returned to pre-infection levels of richness and phylogenetic diversity. In contrast, during the cool-dry season, Bd infections kept increasing through time, and bacterial diversity remained constant. Our findings confirm that infection outcome not only depends on abiotic factors, but also on biotic interactions between hosts and their associated bacterial communities.
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Acknowledgements
We thank AE Ellison, MM Gray and C McDonald for harvesting and shipping Bd zoospores, and help in the lab. AL López-Torres, D Rodriguez, BB Johnson, CA Rodríguez-Gómez, M Longo, D Cancel and M Rodríguez-Medina provided invaluable help in the field by capturing frogs or by assisting during the mesocosm experiment. We also thank PA Burrowes and RL Joglar for access to the lab at the University of Puerto Rico. LM Johnson (Cornell University Statistical Consulting Unit) helped develop the regression models for this study. The Lips Lab at University of Maryland, I Hewson at Cornell University and three anonymous referees provided valuable comments and edits on earlier versions of this manuscript. Grants from the National Science Foundation Evolutionary Processes (DEB-1120249 to KRZ) and Doctoral Dissertation Improvement (DEB-1310036 to KRZ and AVL) programs provided support for this study. AVL was supported by the following fellowships and grants: Ford Foundation Predoctoral Fellowship, Cornell University (CU) SUNY/Sage Diversity Fellowships, CU Department of Ecology and Evolutionary Biology Grants, CU Graduate School Travel Grant, Andrew W. Mellon Graduate Student Grants and Atkinson’s Center for Sustainable Biodiversity Fund.
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Longo, A., Zamudio, K. Environmental fluctuations and host skin bacteria shift survival advantage between frogs and their fungal pathogen. ISME J 11, 349–361 (2017). https://doi.org/10.1038/ismej.2016.138
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DOI: https://doi.org/10.1038/ismej.2016.138
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