Skin bacteriome structure and Batrachochytrium dendrobatidis prevalence differs among two sympatric salamanders in the San Francisco Bay Area

The link between health and host-associated microbiome structure raises the need to identify and quantify factors that influence host-symbiont relationships. Microbial surveys are becoming an important component of wildlife health research, especially in cases where environmental change and infectious diseases are serious issues. Within amphibians, Batrachochytrium sp. is a fatal pathogen that has impacted the population health of numerous species. Bacteria from the skin of amphibians has been characterized to release metabolites that can inhibit the growth of Bd in vivo. We assessed the skin bacteriome, prevalence of Batrachochytrium dendrobatidis, and body conditions of two salamander species with different life histories: the California slender salamander (Batrachoseps attenuatus) and members of the Pacific newt species complex (Taricha torosa and Taricha granulosa). We used 16S rRNA V4 amplicon sequencing to characterize the bacterial communities. Taricha sp. had higher prevalence and loads of Bd compared to Batrachoseps attenuatus, although the prevalence of Bd was restricted to three of the regions tested. Both salamander types possessed similar bacterial community richness, and the composition of the skin bacteriome varied mostly by region. However, we did find certain associations between the salamander species and certain ASVs with mostly members of the family Burkholderiales driving the difference. Our results provide additional evidence for the presence of structure in Bd prevalence and bacteriome structure among sympatric amphibians that inhabit different microhabitats.