Viscosin-like lipopeptides from frog skin bacteria inhibit Aspergillus fumigatus and Batrachochytrium dendrobatidis detected by imaging mass spectrometry and molecular networking

Abstract

Amphibian populations worldwide have declined and in some cases become extinct due to chytridiomycosis, a pandemic disease caused by the fungus Batrachochytrium dendrobatidis ; however, some species have survived these fungal epidemics. Previous studies have suggested that the resistance of these species is due to the presence of cutaneous bacteria producing antifungal metabolites. As our understanding of these metabolites is still limited, we assessed the potential of such compounds against human-relevant fungi such as Aspergillus . In this work we isolated 201 bacterial strains from fifteen samples belonging to seven frog species collected in the highlands of Panama and tested them against Aspergillus fumigatus . Among the 29 bacterial isolates that exhibited antifungal activity, Pseudomonas cichorii showed the greatest inhibition. To visualize the distribution of compounds and identify them in the inhibition zone produced by P. cichorii , we employed MALDI imaging mass spectrometry (MALDI IMS) and MS/MS molecular networking. We identified viscosin and massetolides A, F, G and H in the inhibition zone. Furthermore, viscosin was isolated and evaluated in vitro against A. fumigatus and B. dendrobatidis showing MIC values of 62.50 µg/mL and 31.25 µg/mL, respectively. This is the first report of cyclic depsipeptides with antifungal activity isolated from frog cutaneous bacteria.

Metabolites from Microbes Isolated from the Skin of the Panamanian Rocket Frog Colostethus panamansis (Anura: Dendrobatidae)

“…As C. panamansis is found in riparian habitats, a few meters from the water’s edge and under rocks, this may explain why the skin-associated bacteria in our samples mainly belong to the phylum Proteobacteria [ 46 , 48 ]. The high prevalence of this phylum was observed in other studies where culture-dependent and culture-independent approaches for bacterial identification were applied [ 22 , 46 , 49 , 50 , 51 ]. In terms of bacterial families, specimens of C. panamansis from the General de División Omar Torrijos Herrera National Park, in central Panama, mainly harbored cultivable bacteria of the families Enterobacteriaceae, Comamonadaceae, Aeromonadaceae, Staphylococcaceae and Pseudomonadaceae.…”

“…and Aeromonadaceae ( Aeromonas sp.) were the most abundant bacterial families [ 22 , 46 , 49 , 50 , 51 ]. Although few studies have been carried out in tropical regions, such differences could be attributed to distinct genomic approaches applied (culture-dependent vs. culture independent), sampling sites, sampling size, host specimens and even host-susceptibility to Bd [ 22 , 46 , 52 ].…”

“…It was hypothesized that healthy frogs of this species could harbor bacterial symbionts on their skin as potential producers of specialized metabolites that could protect them against microbial pathogens [ 14 , 15 , 16 , 17 , 18 , 19 ]. While a small number of specialized metabolites produced by amphibian skin-associated bacteria has been reported, including some endowed with antifungal activity against Bd in vitro [ 17 , 20 , 21 , 22 ], multi-omics methods are needed to investigate the symbiotic metabolome of bacteria on the amphibian’s skin mucosome [ 23 ].…”

New Benthic Cyanobacteria from Guadeloupe Mangroves as Producers of Antimicrobials

“…task=9581427a15b7422d8bd2b3b4b086189e&view=view_all_annotations_DB). To further expand the annotation coverage, we applied DEREPLICATOR, a recently developed dereplication algorithm that enables high-throughput peptide natural products (PNPs) identification from their tandem mass spectra [14][15][16][17]. Interestingly, this tool allows to putatively identify an unknown PNP from its known variants (for example, with a substitution, a modification or an adduct) through the so-called variable dereplication process (as opposed to the strict dereplication when a PNP is described in the database).…”

Evaluation of the bacterial and fungal microbiome on the skin of Anaxyrus boreas, Rhinella marina, and Xenopus laevis and implications related to Batrachochytrium dendrobatidis susceptibility

“…B. Harris et al, 2006) Pseudomonas Yes (Becker et al, 2015;Catenazzi et al, 2018;J. B. Harris et al, 2006;Jiménez et al, 2019;Loudon et al, 2014;Martin H et al, 2019;Muletz-Wolz et al, 2017;Myers et al, 2012) Sphingobium No evidence…”