Panamanian frog species host unique skin bacterial communities

Abstract

Vertebrates, including amphibians, host diverse symbiotic microbes that contribute to host disease resistance. Globally, and especially in montane tropical systems, many amphibian species are threatened by a chytrid fungus, Batrachochytrium dendrobatidis (Bd), that causes a lethal skin disease. Bd therefore may be a strong selective agent on the diversity and function of the microbial communities inhabiting amphibian skin. In Panamá, amphibian population declines and the spread of Bd have been tracked. In 2012, we completed a field survey in Panamá to examine frog skin microbiota in the context of Bd infection. We focused on three frog species and collected two skin swabs per frog from a total of 136 frogs across four sites that varied from west to east in the time since Bd arrival. One swab was used to assess bacterial community structure using 16S rRNA amplicon sequencing and to determine Bd infection status, and one was used to assess metabolite diversity, as the bacterial production of anti-fungal metabolites is an important disease resistance function. The skin microbiota of the three Panamanian frog species differed in OTU (operational taxonomic unit, ~bacterial species) community composition and metabolite profiles, although the pattern was less strong for the metabolites. Comparisons between frog skin bacterial communities from Panamá and the US suggest broad similarities at the phylum level, but key differences at lower taxonomic levels. In our field survey in Panamá, across all four sites, only 35 individuals (~26%) were Bd infected. There was no clustering of OTUs or metabolite profiles based on Bd infection status and no clear pattern of west-east changes in OTUs or metabolite profiles across the four sites. Overall, our field survey data suggest that different bacterial communities might be producing broadly similar sets of metabolites across frog hosts and sites. Community structure and function may not be as tightly coupled in these skin symbiont microbial systems as it is in many macro-systems.

Diversity and stability of egg‐bacterial assemblages: The role of paternal care in the glassfrog Hyalinobatrachium colymbiphyllum

“…, Belden et al . ). To assess temporal changes in bacterial community diversity, we swabbed each clutch two times: once 2.5 days after oviposition and again 5.5 days after oviposition, which is approximately 1.5 days prior to hatching competence for this population (J. Delia, unpubl.…”

Direct and Indirect Horizontal Transmission of the Antifungal Probiotic Bacterium Janthinobacterium lividum on Green Frog (Lithobates clamitans) Tadpoles

“…In this study, we tracked the presence and abundance of the probiotic bacterium J. lividum through time using two different techniques: bacterial culturing using selective media for rifampin-resistant strains (33) and 16S amplicon sequencing, which is a culture-independent technique increasingly used to describe the bacterial community structure in amphibians (14,45,58,68,69). Despite the great advantages of using 16S amplicon sequencing for community profiling, one caveat is that this method does not distinguish between the natural J. lividum and the rifampin-resistant inoculated strain.…”

“…In this study, we identified 5,981 bacterial OTUs on L. clamitans skin, and these communities were dominated by two Pseudomonas OTUs. Several members of the genus Pseudomonas are known to produce antifungal and antibiotic compounds, and their dominance on the amphibian skin may indicate a defensive function (14,31,45,69,71). A recent study on Bufo boreas boreas tadpoles that compared bacterial taxa with a B. dendrobatidis-inhibitory bacterial OTU database found that tadpoles hosted significantly more inhibitory OTUs than other life stages or environmental samples (46).…”

“…B. dendrobatidis has caused extinctions of amphibian species in the tropics, including tropical Australia (10) and the Neotropics in Central America (11,12). However, some species are considered resistant or tolerant since they are persisting in the wild despite the presence of the pathogen (13,14). In order to reduce the risk of population declines or extinctions in susceptible amphibians, effective mitigation protocols must be developed.…”

The Influence of Brazilian Biodiversity on Searching for Human Use Pharmaceuticals

“…This paper should be read in conjunction with two others that show how the Panamanian frogs which had experienced a lethal fungal infection, have now overcome the infection via commensal microbes. 64,65 What was not mentioned however, is that these vertebrates contain toxins that almost certainly are adsorbed from their diet of specific ants.…”