Foam nest construction is a unique oviposition method that evolved independently in anurans lineages from the Neotropics, Asia, and Africa. The nest’s formation involves protein secretions from the oviduct follow by a series of fast kicking of the hind legs by the amplectant pair. One of their potential functions is protection against pathogens, but with a lack of supportive evidence. In this sense, the overall aims of our project is to understand whether skin’s antimicrobial peptides (AMPs), produced by dermal glands may be incorporated to the foam during nest formation and modulate its microbiome. This study represents the first steps on this regard. Here, we analyzed transcriptomes from dorsal skin region of a male and a female of Physalaemus santafecinus to assess AMP gene expression. To assemble the transcriptome, we used Trinity and Spades, and Transdecoder and Orfpredictor for translation. Using conserved sequences from the signal peptide region of described prepro-peptides in amphibians, over 40 mature peptides were found in male, 37 in the female, and only 2 in oviduct. The two peptides expressed in the oviduct were also present in skin of both sexes. More than 10 peptides were expressed in both sexes, and other several exhibited similar sequences. These are newly described peptides, sharing <50% similarity with the 3569+ AMPs in the APD (Antimicrobial Peptide Database). Physicochemical analysis revealed varied charges, hydrophobicity, and 3D structures. This transcriptomic characterization of Physalaemus santafecinus skin, coupled with biochemical and microbiological data, offers crucial insights into reproductive mechanism and the role of secretions in foam nest construction.

Biofilms in chronic wounds, including diabetic foot ulcers, pressure ulcers, and venous leg ulcers, pose a major challenge to wound management. Herein, we report a Janus-type antimicrobial dressing for eradication of biofilms in chronic wounds. The dressing consists of electrospun nanofiber membranes coupled with dissolvable microneedle arrays to enable effective delivery of a database-designed antimicrobial peptide to both inside and outside biofilms. This antimicrobial dressing exhibited high efficacy against a broad spectrum of resistant pathogens in vitro. Importantly, such a dressing was able to eradicate methicillin resistant Staphylococcus aureus (MRSA) biofilms in both an ex vivo human skin wound infection model and a type II diabetic mouse wound infection model after daily treatment without applying surgical debridement. Most importantly, the dressing can also completely remove the Pseudomonas aeruginosa and MRSA, dual-species biofilm in an ex vivo human skin infection model. In addition, our computational simulations also suggested that microneedles were more effective in the delivery of peptides to the biofilms than free drugs. Our results indicate that the Janus-type antimicrobial dressings may provide an effective treatment and management of chronic wound polymicrobial infections.

Antimicrobial peptides (AMPs) have emerged as a promising approach in the development of antibiotics. In contrast to traditional chemical-based antibiotics, AMPs exert their effects through a "physical" mechanism. Specific AMPs have the capability to physically disrupt the cell membrane of bacteria, leading to their demise. Nevertheless, it is crucial to consider the interaction between AMPs and normal cells. AMPs that indiscriminately eliminate all types of cells cannot be employed as pharmaceuticals, as they would also interfere with the regular physiological functions within our bodies.

The primary goal of this study is to mitigate the extent of hemolysis caused by the synthesized AMP sequences. Computational methods are employed to identify potential AMP sequences, as this approach proves to be cost-effective compared to the actual synthesis of the sequences. Hence, the early screening of sequences with the potential to induce hemolysis offers distinct advantages.

To accomplish this, a variety of ensemble classification models were constructed to ascertain whether a peptide sequence would induce a particular degree of hemolysis under specified peptide concentrations based on the dataset form DBAASP. These models were developed by integrating diverse machine learning techniques, including support vector machines, random forests, AdaBoost, multilayer perceptron, k-nearest neighbors, and XGBoost. In general, the results of this study demonstrate an accuracy of approximately 0.82, 0.8 and 0.81 in predicting whether a peptide sequence is hemolytic under a 10%, 20% and 40% hemolysis threshold, respectvely.

The secretion of amphibians has been used for many years for different purposes such as religion, culture, agro-economics or even as therapeutic agents. Although these secretions are a mixture of different molecules, especially the active peptides therein have been studied intensively during the past 30 years. Peptides have shown to be able to inhibit the growth of different human microorganisms (making from them good candidates for potential therapeutic agents), and soil microorganisms. The objectives of this work was to analyze the secretion of Leptodactylus labyrinthicus in order to identify bioactive peptides, with emphasis on their biological activity in an ecological context. Results reported here shown that, when fractioning the skin secretion of L. labyrinthicus, the growth of Staphylococcus aureus and Burkholderia cepacia were slowly delayed by fractions 8 and 9, but not any delaying effect was observed on Escherichia coli. Interestingly, the whole secretion, have shown a growth promotion for Burkholderia cepacia, but not any effect on Staphylococcus aureus and Escherichia coli. In addition, two peptides already described in the literature, known as Pentadactylin (which inhibit E. coli, P. aeruginosa and S. aureus), and Ocellatin-F1 (which inhibit E.coli and P. aeruginosa), were found in fractions 8 and 9 of this frog skin secretion. In view of these results we hypothesize that, the secretion of Leptodactylus labyrinthicus is a mix of molecules that act in synergy as a bio-regulator mechanism selecting or benefiting microorganisms on the frog’s skin population for ecological, immunological or other purposes not well understood to the moment.

Amphibian skin secretion has been an important source of broad-spectrum and membrane-targeting antimicrobial peptides, which promise to tackle the antibiotic resistance crisis.Callimedusa ecuatoriana from Ecuador is an example of an unexplored species, that can hold a library of novel chemical scaffolds with antibiotic action. In this study, we report a novel skin peptide (PTR-CE1) identified by molecular cloning of mRNA precursor. We demonstrated that it lacks of antimicrobial activity. So, using the natural sequence of PTR-CE1 as a template, we designed and synthesized two analogs (PTR-CE1a and PTR-CE1b). Both engineered peptides displayed high antibacterial activity, even against the ampicillin-resistant bacterial strains. While PTR-CE1b showed MIC values of 106.5-212.99 mM and less than 10% of damage to red blood cells at 3.02 mM, PTR-CE1a displayed a more potent broad-spectrum effect against all the tested microorganisms, with MIC values of 3.02-12.06 mM, and low hemolytic properties at 6.66 mM. This study highlights the role of the secondary structure for antimicrobial activity and shows how inactive peptides can be useful as a template for the generation of new molecules with high activity and low toxicity.