Successful Transmission and Isolation of a Fungal Pathogen From Wild Frogs to a Captive Amphibian Model Species: Fine Scale Pathogen Genetic Diversity and Infection-Induced Changes in Skin Bacteria

Abstract

Amphibian populations worldwide are severely threatened, in part, by the pathogenic fungus Batrachochytrium dendrobatidis (Bd). While Bd has driven many amphibian declines and extinctions, its impact varies, with some populations exhibiting resistance or tolerance. Understanding the mechanisms behind this variation, together with Bd genetic diversity, is crucial for conservation. We used the model organism Hymenochirus boettgeri in a lab-based transmission experiment designed to isolate Bd derived from wild amphibian hosts with low pathogen loads. Through successful transmission and subsequent isolation and genotyping, we identified multiple Bd genotypes from a single population, including a potential sexual recombinant, all belonging to the Global Panzootic Lineage (Bd-GPL). This finding contributes to evidence of ongoing genetic mixing of Bd in natural environments. Additionally, we leveraged this experiment to assess Bd-induced changes in amphibian skin bacteria. Our results showed significant changes in the skin bacterial communities of H. boettgeri after acquiring Bd infection, including reductions in bacterial diversity, and shifts in community composition, as observed in others susceptible species. These findings highlight the value of transmission experiments in isolating Bd from wild hosts and underscore the potential of H. boettgeri as a model to investigate Bd genetic diversity and host-associated microbiome responses to infection.