# Associations between skin bacteria and chytrid fungal infection in Asian amphibians

## TL;DR

Asian amphibians resist a deadly skin fungus, possibly due to protective bacteria on their skin.

## Contribution

Identified specific bacterial OTUs associated with resistance to Bd infection in Asian amphibians.

## Key findings

- Asian amphibians showed resistance to Bd infection in experiments.
- Alpha diversity and 16 OTUs of skin bacteria were linked to lower Bd loads.
- Four bacterial OTUs were consistently enriched in Asian amphibians compared to a susceptible species.

## Abstract

Identifying the generality of defensive symbionts and microbiome structures associated with pathogen infection across multiple hosts provides insights into understanding disease susceptibility and managing disease. The fungus Batrachochytrium dendrobatidis (Bd) infects amphibian skin (the disease, chytridiomycosis), causing amphibian declines worldwide except in Asia. Here, we investigated associations between amphibian skin bacterial microbiome and Bd infection in five Asian amphibian species and the susceptible, Australasian species Litoria caerulea via experiments and in the wild. We found that Asian amphibians showed resistance to Bd infection experimentally, with Bd infection causing divergence in microbiome structures in inoculated animals. Alpha diversity and relative abundances of 16 OTUs had negative effects on Bd load across inoculated animals. Compared with L. caerulea, four OTUs (Bradyrhizobium, Achromobacter, Sediminibacterium, and Rhodoplanes) with negative effects on Bd load were consistently enriched in experimental and wild populations of Asian amphibians. These OTUs are probably associated with reduced Bd loads in Asian amphibians.

•Batrachochytrium dendrobatidis (Bd) infects amphibian skin, causing their decline except in Asia•Asian amphibians showed resistance to the fungal Bd infection in laboratory experiments•α diversity and 16 OTUs of the skin bacterial microbiome were negatively associated with Bd load•Four OTUs likely provided protection against the Bd infection in Asian amphibians

Batrachochytrium dendrobatidis (Bd) infects amphibian skin, causing their decline except in Asia

Asian amphibians showed resistance to the fungal Bd infection in laboratory experiments

α diversity and 16 OTUs of the skin bacterial microbiome were negatively associated with Bd load

Four OTUs likely provided protection against the Bd infection in Asian amphibians

Ecology; Zoology; Microbiology