surviving chytridiomycosis differential anti-batrachochytrium dendrobatidis activity in bacterial isolates from three lowland species of atelopus幸存的壶微分anti-batrachochytrium细菌分离菌的活动三个atelopus低地物种.pdf

Surviving Chytridiomycosis: Differential Anti- Batrachochytrium dendrobatidis Activity in Bacterial Isolates from Three Lowland Species of Atelopus ¤ ´ Sandra V. Flechas*, Carolina Sarmiento , Martha E. Cardenas, Edgar M. Medina, Silvia Restrepo, ´ Adolfo Amezquita ´ Department of Biological Sciences, Universidad de los Andes, Bogota, Colombia Abstract In the Neotropics, almost every species of the stream-dwelling harlequin toads (genus Atelopus) have experienced catastrophic declines. The persistence of lowland species of Atelopus could be explained by the lower growth rate of Batrachochytrium dendrobatidis (Bd) at temperatures above 25uC. We tested the complementary hypothesis that the toads’ skin bacterial microbiota acts as a protective barrier against the pathogen, perhaps delaying or impeding the symptomatic phase of chytridiomycosis. We isolated 148 cultivable bacterial strains from three lowland Atelopus species and quantified the anti-Bd activity through antagonism assays. Twenty-six percent (38 strains representing 12 species) of the bacteria inhibited Bd growth and just two of them were shared among the toad species sampled in different localities. Interestingly, the strongest anti-Bd activity was measured in bacteria isolated from A. elegans, the only species that tested positive for the pathogen. The cutaneous bacterial microbiota is thus likely a fitness-enhancing trait that may (adaptation) or not (exaptation) have appeared because of natural selection mediated by chytridiomycosis. Our findings reveal bacterial strains for development of local probiotic treatments against chytridiomycos