Diverse communities of bacteria have been identified on the skin of amphibians around the world and some of these bacterial species have been implicated in the protection of amphibians from Batrachochytrium dendrobatidis (Bd). Plethodon cinereus is a common salamander species whose cutaneous bacteria have been characterized by multiple species with Bd-inhibitory abilities. It is known that bacterial communities can vary drastically over short distances and across levels of land use change. To determine if P. cinereus cutaneous bacterial communities vary over space and land use, we sampled 55 salamanders from 8 sites along an 80 km urban-to-rural gradient from Bronx to Putnam counties in New York during Fall 2016 and Spring 2017. Swabs were used to collect cutaneous bacteria from salamander left, right, and ventral sides and were immediately streaked onto LB agar plates and incubated at 18°C for three days. Bacteria were isolated morphologically and Sanger sequenced with the 515F/806R primer pair. Species were identified using the EzBioCloud database and were challenged with Bd to characterize anti-fungal ability following standard spectrophotometric assay protocols.
Results/Conclusions
From 55 salamanders, 156 isolates were found identifying as 78 bacterial species from 27 genera. Similar to other amphibian studies, all bacterial communities were dominated by Proteobacteria (>80% of species). Acinetobacteria were only present on suburban individuals and Bacteroidetes were absent from rural individuals. Pseudomonas was the most abundant bacterial genus (18 species) found on 28/55 salamanders at all sites along the gradient. Bacteria varied in their ability to inhibit Bd ranging from -19.4-100% inhibition, and varied among species within some genera. Anti-Bd bacteria, such as Lysobacter gummosus and Janthinobacterium lividum, previously identified on P. cinereus in other regions were absent from all salamanders sampled in this study. However, Stenotrophomonas rhizophila, a species found on salamanders at every site, had the highest anti-fungal ability of all isolates tested (mean = 93%) and is as inhibitory as J. lividum (t-test, p>0.05). Overall, our results suggest that the cutaneous community varies with space and land use change, and anti-Bd abilities are shared across multiple bacterial genera but vary among bacterial species, agreeing with past studies.