The Fungicide Chlorothalonil Changes the Amphibian Skin Microbiome: A Potential Factor Disrupting a Host Disease-Protective Trait

Randall R Jiménez,Clemens Ruepert,Erick Ballestero,Simone Sommer,Gilbert Alvarado

doi:10.3390/applmicrobiol1010004

Abstract

The skin microbiome is an important part of amphibian immune defenses and protects against pathogens such as the chytrid fungus Batrachochytrium dendrobatidis (Bd), which causes the skin disease chytridiomycosis. Alteration of the microbiome by anthropogenic factors, like pesticides, can impact this protective trait, disrupting its functionality. Chlorothalonil is a widely used fungicide that has been recognized as having an impact on amphibians, but so far, no studies have investigated its effects on amphibian microbial communities. In the present study, we used the amphibian Lithobates vibicarius from the montane forest of Costa Rica, which now appears to persist despite ongoing Bd-exposure, as an experimental model organism. We used 16S rRNA amplicon sequencing to investigate the effect of chlorothalonil on tadpoles’ skin microbiome. We found that exposure to chlorothalonil changes bacterial community composition, with more significant changes at a higher concentration. We also found that a larger number of bacteria were reduced on tadpoles’ skin when exposed to the higher concentration of chlorothalonil. We detected four presumed Bd-inhibitory bacteria being suppressed on tadpoles exposed to the fungicide. Our results suggest that exposure to a widely used fungicide could be impacting host-associated bacterial communities, potentially disrupting an amphibian protective trait against pathogens.

Highlights

Introduction iationsAmphibians around the world are increasingly threatened by diseases caused by fungi, viruses, bacteria, and parasites [1,2]
Pairwise PERMANOVA tests indicated significant differences in the bacterial community composition between the tadpoles kept in the solvent control and the treatment with a high concentration of the fungicide, whereas those between solvent control and the treatment with a low concentration were similar (Table 1)
The present study highlights the impact of chlorothalonil, a widely frog usedthat fungicide, the immunologically important skin microbial community of a threatened persists on the immunologically important skin microbial community of a threatened frog that despite ongoing exposure to Batrachochytrium dendrobatidis (Bd)

Summary

Introduction

Introduction iationsAmphibians around the world are increasingly threatened by diseases caused by fungi, viruses, bacteria, and parasites [1,2]. The infectious skin disease, chytridiomycosis, is one of the main diseases impacting amphibian health [3,4]. This disease caused by the chytrid fungal pathogens Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal) can cause mass die-offs in amphibian species [5,6]. The skin microbiome is considered one of the first lines of defense against pathogenic infections and can mediate disease susceptibility [7,8,9], suggesting it is an essential part of the amphibian’s innate immune system.

Methods

Results

Conclusion