# Community Structure and Function of Amphibian Skin Microbes: An Experiment with Bullfrogs Exposed to a Chytrid Fungus

## TL;DR

This study shows that the skin microbes of bullfrogs can influence their resistance to a deadly fungal disease.

## Contribution

The study demonstrates that pre-existing microbial community structure affects infection outcomes in amphibians exposed to a chytrid fungus.

## Key findings

- Frog skin microbial community structure before exposure influenced Bd infection intensity.
- Bd exposure altered microbial community structure and function in manipulated groups.
- Higher Bd infection was negatively correlated with frog growth.

## Abstract

The vertebrate microbiome contributes to disease resistance, but few experiments have examined the link between microbiome community structure and disease resistance functions. Chytridiomycosis, a major cause of amphibian population declines, is a skin disease caused by the fungus, Batrachochytrium dendrobatidis (Bd). In a factorial experiment, bullfrog skin microbiota was reduced with antibiotics, augmented with an anti-Bd bacterial isolate (Janthinobacterium lividum), or unmanipulated, and individuals were then either exposed or not exposed to Bd. We found that the microbial community structure of individual frogs prior to Bd exposure influenced Bd infection intensity one week following exposure, which, in turn, was negatively correlated with proportional growth during the experiment. Microbial community structure and function differed among unmanipulated, antibiotic-treated, and augmented frogs only when frogs were exposed to Bd. Bd is a selective force on microbial community structure and function, and beneficial states of microbial community structure may serve to limit the impacts of infection.