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A fungal pathogen of amphibians, Batrachochytrium dendrobatidis, attenuates in pathogenicity with in vitro passages.

Langhammer PF, Lips KR, Burrowes PA, Tunstall T, Palmer CM, Collins JP - PLoS ONE (2013)

Bottom Line: This difference in zoospore production was associated with a difference in pathogenicity for a susceptible amphibian species, indicating that fecundity may be an important virulence factor for Bd.We hypothesize that the differences in phenotypic performance observed with Atelopus zeteki are rooted in changes of the Bd genome.Future investigations enabled by this study will focus on the underlying mechanisms of Bd pathogenicity.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America.

ABSTRACT
Laboratory investigations into the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), have accelerated recently, given the pathogen's role in causing the global decline and extinction of amphibians. Studies in which host animals were exposed to Bd have largely assumed that lab-maintained pathogen cultures retained the infective and pathogenic properties of wild isolates. Attenuated pathogenicity is common in artificially maintained cultures of other pathogenic fungi, but to date, it is unknown whether, and to what degree, Bd might change in culture. We compared zoospore production over time in two samples of a single Bd isolate having different passage histories: one maintained in artificial media for more than six years (JEL427-P39), and one recently thawed from cryopreserved stock (JEL427-P9). In a common garden experiment, we then exposed two different amphibian species, Eleutherodactylus coqui and Atelopus zeteki, to both cultures to test whether Bd attenuates in pathogenicity with in vitro passages. The culture with the shorter passage history, JEL427-P9, had significantly greater zoospore densities over time compared to JEL427-P39. This difference in zoospore production was associated with a difference in pathogenicity for a susceptible amphibian species, indicating that fecundity may be an important virulence factor for Bd. In the 130-day experiment, Atelopus zeteki frogs exposed to the JEL427-P9 culture experienced higher average infection intensity and 100% mortality, compared with 60% mortality for frogs exposed to JEL427-P39. This effect was not observed with Eleutherodactylus coqui, which was able to clear infection. We hypothesize that the differences in phenotypic performance observed with Atelopus zeteki are rooted in changes of the Bd genome. Future investigations enabled by this study will focus on the underlying mechanisms of Bd pathogenicity.

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Related in: MedlinePlus

Mean infection intensity for (a) Eleutherodactylus coqui and (b) Atelopus zeteki frogs exposed to JEL427-P9 or JEL427-P39.
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pone-0077630-g003: Mean infection intensity for (a) Eleutherodactylus coqui and (b) Atelopus zeteki frogs exposed to JEL427-P9 or JEL427-P39.

Mentions: On day 15 post-exposure, infection prevalence among E. coqui frogs was 67% in the JEL427-P9 group and 75% in the JEL427-P39 group, indicating that not all frogs became infected during exposure (Figure 2a). Prevalence after day 15 dropped sharply, as frogs started clearing infection despite the large exposure dose. The results of the mixed effects model indicate no significant difference in mean infection intensity (Figure 3a) over time between the two groups (-0.937 log genomic equivalents, p=0.15). Finally, there was no significant difference in mortality between the three treatment groups, including the controls (Log-rank test, p=0.37). Only 1 frog died during the experiment, from the JEL427-P39 group. The frog may have succumbed to chytridiomycosis given its relatively high pathogen load (12,816 zoospore genomic equivalents), but all other Bd-exposed frogs cleared infection within 80 days.


A fungal pathogen of amphibians, Batrachochytrium dendrobatidis, attenuates in pathogenicity with in vitro passages.

Langhammer PF, Lips KR, Burrowes PA, Tunstall T, Palmer CM, Collins JP - PLoS ONE (2013)

Mean infection intensity for (a) Eleutherodactylus coqui and (b) Atelopus zeteki frogs exposed to JEL427-P9 or JEL427-P39.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3795048&req=5

pone-0077630-g003: Mean infection intensity for (a) Eleutherodactylus coqui and (b) Atelopus zeteki frogs exposed to JEL427-P9 or JEL427-P39.
Mentions: On day 15 post-exposure, infection prevalence among E. coqui frogs was 67% in the JEL427-P9 group and 75% in the JEL427-P39 group, indicating that not all frogs became infected during exposure (Figure 2a). Prevalence after day 15 dropped sharply, as frogs started clearing infection despite the large exposure dose. The results of the mixed effects model indicate no significant difference in mean infection intensity (Figure 3a) over time between the two groups (-0.937 log genomic equivalents, p=0.15). Finally, there was no significant difference in mortality between the three treatment groups, including the controls (Log-rank test, p=0.37). Only 1 frog died during the experiment, from the JEL427-P39 group. The frog may have succumbed to chytridiomycosis given its relatively high pathogen load (12,816 zoospore genomic equivalents), but all other Bd-exposed frogs cleared infection within 80 days.

Bottom Line: This difference in zoospore production was associated with a difference in pathogenicity for a susceptible amphibian species, indicating that fecundity may be an important virulence factor for Bd.We hypothesize that the differences in phenotypic performance observed with Atelopus zeteki are rooted in changes of the Bd genome.Future investigations enabled by this study will focus on the underlying mechanisms of Bd pathogenicity.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America.

ABSTRACT
Laboratory investigations into the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), have accelerated recently, given the pathogen's role in causing the global decline and extinction of amphibians. Studies in which host animals were exposed to Bd have largely assumed that lab-maintained pathogen cultures retained the infective and pathogenic properties of wild isolates. Attenuated pathogenicity is common in artificially maintained cultures of other pathogenic fungi, but to date, it is unknown whether, and to what degree, Bd might change in culture. We compared zoospore production over time in two samples of a single Bd isolate having different passage histories: one maintained in artificial media for more than six years (JEL427-P39), and one recently thawed from cryopreserved stock (JEL427-P9). In a common garden experiment, we then exposed two different amphibian species, Eleutherodactylus coqui and Atelopus zeteki, to both cultures to test whether Bd attenuates in pathogenicity with in vitro passages. The culture with the shorter passage history, JEL427-P9, had significantly greater zoospore densities over time compared to JEL427-P39. This difference in zoospore production was associated with a difference in pathogenicity for a susceptible amphibian species, indicating that fecundity may be an important virulence factor for Bd. In the 130-day experiment, Atelopus zeteki frogs exposed to the JEL427-P9 culture experienced higher average infection intensity and 100% mortality, compared with 60% mortality for frogs exposed to JEL427-P39. This effect was not observed with Eleutherodactylus coqui, which was able to clear infection. We hypothesize that the differences in phenotypic performance observed with Atelopus zeteki are rooted in changes of the Bd genome. Future investigations enabled by this study will focus on the underlying mechanisms of Bd pathogenicity.

Show MeSH
Related in: MedlinePlus