The contribution of skin antimicrobial peptides to the system of innate immunity in anurans

Abstract

Cationic peptides with the propensity to adopt an amphipathic α-helical conformation in a membrane-mimetic environment are synthesized in the skins of many species of anurans (frogs and toads). These peptides frequently display cytolytic activities against a range of pathogenic bacteria and fungi consistent with the idea that they play a role in the host's system of innate immunity. However, the importance of the peptides in the survival strategy of the animal is not clearly understood. It is a common misconception that antimicrobial peptides are synthesized in the skins of all anurans. In fact, the species distribution is sporadic suggesting that their production may confer some evolutionary advantage to the organism but is not necessary for survival. Although growth inhibitory activity against the chytrid fungus Batrachochytrium dendrobatidis, responsible for anuran population declines worldwide, has been demonstrated in vitro, the ability of frog skin antimicrobial peptides to protect the animal in the wild appears to be limited and there is no clear correlation between their production by a species and its resistance to fatal chytridiomycosis. The low potency of many frog skin antimicrobial peptides is consistent with the hypothesis that cutaneous symbiotic bacteria may provide the major system of defense against pathogenic microorganisms in the environment with antimicrobial peptides assuming a supplementary role in some species.

Characteristics of meiofauna in extreme marine ecosystems: a review

“…cuticular exoskeleton or shell) to physically protect their underlying tissues from direct biotic/abiotic interactions are particularly suited to studying the adaptation of external immunity to changing and harsh environmental conditions. Rather than physical protection, annelids have developed a strong external immunity based on the production of mucus and AMPs by the epidermic cells that respectively trap and kill/select pathogenic/symbiotic bacteria (Salzet et al 2006;Tasiemski and Salzet 2010;Conlon 2011;Gallo and Nakatsuji 2011). For instance, polychaetes produce original AMPs, some of which are restricted to just one worm family (e.g.…”

Composition of symbiotic bacteria predicts survival in Panamanian golden frogs infected with a lethal fungus

“…Our methods for chemical analysis (reverse-phase LCMS) have been optimized for observation of bacterial metabolites [36]. Many known metabolites of amphibian origin that inhibit pathogens and provide defence against predators, such as antimicrobial peptides [62] and zetekitoxin [63], respectively, are too polar to be observed in our conditions. Antimicrobial peptides have not been detected in captive A. zeteki (B. Sheafor 2014, personal communication).…”

Screening bacterial metabolites for inhibitory effects against Batrachochytrium dendrobatidis using a spectrophotometric assay

“…Symbiotic microbes can therefore be regarded as another component of amphibians' innate immune defence mechanisms (Woodhams et al 2007b, Walke et al 2011. Symbiotic bacteria resident on anuran skin may sometimes play a greater role than AMPs in defence against Bd, and AMP potency may be attenuated in species that rely heavily on their beneficial microbiota (Conlon 2011). Harris et al (2006) first demonstrated in vitro inhibition of Bd by a number of bacterial species isolated from the skin of salamanders, and suggested that Bdinhibiting bacteria could be used as a bioaugmentation tool to confer disease resistance to vulnerable amphibian populations.…”