The fungal skin infection, Batrachochytrium dendrobatidis (Bd), has pushed many amphibian species to the brink of extinction. One such species, the Panamanian golden frog, is likely extinct in the wild and has been maintained in captive breeding colonies since 2006. Successful reintroduction of this species hinges on the ability of the amphibians to fight off Bd infection.
A new study by Matthew Becker and colleagues hints at one possible way in which these animals can survive Bd infections. Becker et al were looking for skin bacteria that were able to inhibit Bd growth in vitro in the hopes of finding a few microbes that could be used as a microbial “vaccine”. Unfortunately, none of the four bacteria that they applied to the Panamanian golden frogs were able to fight off the Bd infection.
Interestingly, however, they found that ~30% of the subjects still managed to survive the Bd infection. When they tested the initial (i.e., prior to infection) microbial skin composition of these “survivors” (using 16s sequencing) they found that they differed from the animals that succumbed to infection at 23 groups of microbes (i.e., “OTUs“). These “indicator” microbes, however, represented only a tiny fraction of the total microbial skin composition (~2.3%), suggesting that very small proportions of symbiotic bacteria may have large downstream effects on the ability of these amphibians to survive Bd infection.
“the ability to detect microbial community composition differences among survival/infection outcome groups prior to infection…may allow conservationists to predict susceptibility in free-living amphibian populations threatened by Bd.”
P.S. Wikipedia tells me that the name of Panamanian golden frog is a misnomer. They are actually “true toads”.
M. H. Becker, J. B. Walke, S. Cikanek, A. E. Savage, N. Mattheus, C. N. Santiago, K. P. C. Minbiole, R. N. Harris, L. K. Belden, B. Gratwicke. Composition of symbiotic bacteria predicts survival in Panamanian golden frogs infected with a lethal fungus. Proceedings of the Royal Society B: Biological Sciences, 2015; 282 (1805): 20142881 DOI: 10.1098/rspb.2014.2881