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Fil: Ferro, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentina

The hylid tribe Cophomantini is a diverse clade of Neotropical treefrogs composed of the genera Aplastodiscus, Boana, Bokermannohyla, Hyloscirtus, and Myersiohyla. The phylogenetic relationships of Cophomantini have been comprehensively reviewed in the literature, providing a suitable framework for the study of chromosome evolution. Employing different banding techniques, we studied the chromosomes of 25 species of Boana and 3 of Hyloscirtus; thus providing, for the first time, data for Hyloscirtus and for 15 species of Boana. Most species showed karyotypes with 2n = 2x = 24 chromosomes; some species of the B. albopunctata group have 2n = 2x = 22, and H. alytolylax has 2n = 2x = 20. Karyotypes are all bi-armed in most species presented, with the exception of H. larinopygion (FN = 46) and H. alytolylax (FN = 38), with karyotypes that have a single pair of small telocentric chromosomes. In most species of Boana, NORs are observed in a single pair of chromosomes, mostly in the small chromosomes, although in some species of the B. albopunctata, B. pulchella, and B. semilineata groups, this marker occurs on the larger pairs 8, 1, and 7, respectively. In Hyloscirtus, NOR position differs in the three studied species: H. alytolylax (4p), H. palmeri (4q), and H. larinopygion (1p). Heterochromatin is a variable marker that could provide valuable evidence, but it would be necesserary to understand the molecular composition of the C-bands that are observed in different species in order to test its putative homology. In H. alytolylax, a centromeric DAPI+ band was observed on one homologue of chromosome pair 2. The band was present in males but absent in females, providing evidence for an XX/XY sex determining system in this species. We review and discuss the importance of the different chromosome markers (NOR position, C-bands, and DAPI/CMA3 patterns) for their impact on the taxonomy and karyotype evolution in Cophomantini.

Many amphibian species are at risk of extinction in their natural habitats due to the presence of the fungal pathogen Batrachochytrium dendrobatidis ( Bd ). For the most highly endangered species , captive assurance colonies have been established as an emergency measure to avoid extinction. Experimental research has suggested that symbiotic microorganisms in the skin of amphibians play a key role against Bd . While previous studies have addressed the effects of captivity on the cutaneous bacterial community, it remains poorly studied whether and how captive conditions affect the proportion of beneficial bacteria or their anti- Bd performance on amphibian hosts. In this study we sampled three amphibian species of the highly threatened genus, Atelopus , that remain in the wild but are also part of ex situ breeding programs in Colombia and Ecuador. Our goals were to (1) estimate the diversity of culturable bacterial assemblages in these three species of Atelopus , (2) describe the effect of captivity on the composition of skin microbiota, and (3) examine how captivity affects the bacterial ability to inhibit Bd growth. Using challenge assays we tested each bacterial isolate against Bd , and through sequencing of the 16S rRNA gene, we identified species from thirteen genera of bacteria that inhibited Bd growth. Surprisingly, we did not detect a reduction in skin bacteria diversity in captive frogs. Moreover, we found that frogs in captivity still harbor bacteria with anti- Bd activity. Although the scope of our study is limited to a few species and to the culturable portion of the bacterial community, our results indicate that captive programs do not necessarily change bacterial communities of the toad skins in a way that impedes the control of Bd in case of an eventual reintroduction.

Microbial diseases have been declared one of the main threats to humanity, which is why, in recent years, great interest has been generated in the development of nanocomposites with antimicrobial capacity. The present work studied two magnetic nanocomposites based on graphene oxide (GO) and multiwall carbon nanotubes (MWCNTs). The synthesis of these magnetic nanocomposites consisted of three phases: first, the synthesis of iron magnetic nanoparticles (MNPs), second, the adsorption of the photosensitizer menthol-Zinc phthalocyanine (ZnMintPc) into MWCNTs and GO, and the third phase, encapsulation in poly (N-vinylcaprolactam-co-poly(ethylene glycol diacrylate)) poly (VCL-co-PEGDA) polymer VCL/PEGDA a biocompatible hydrogel, to obtain the magnetic nanocomposites VCL/PEGDA-MNPs-MWCNTs-ZnMintPc and VCL/PEGDA-MNPs-GO-ZnMintPc. In vitro studies were carried out using Escherichia coli and Staphylococcus aureus bacteria and the Candida albicans yeast based on the Photodynamic/Photothermal (PTT/PDT) effect. This research describes the nanocomposites’ optical, morphological, magnetic, and photophysical characteristics and their application as antimicrobial agents. The antimicrobial effect of magnetics nanocomposites was evaluated based on the PDT/PTT effect. For this purpose, doses of 65 mW·cm−2 with 630 nm light were used. The VCL/PEGDA-MNPs-GO-ZnMintPc nanocomposite eliminated E. coli and S. aureus colonies, while the VCL/PEGDA-MNPs-MWCNTs-ZnMintPc nanocomposite was able to kill the three types of microorganisms. Consequently, the latter is considered a broad-spectrum antimicrobial agent in PDT and PTT.

Frog skin secretions contain medically-valuable molecules, which are useful for the discovery of new biopharmaceuticals. The peptide profile of the skin secretion of Agalychnis spurrelli has not been investigated; therefore, the structural and biological characterization of its compounds signify an inestimable opportunity to acquire new biologically-active chemical scaffolds. In this work, skin secretion from this amphibian was analysed by molecular cloning and tandem mass spectrometry. Although the extent of this work was not exhaustive, eleven skin secretion peptides belonging to five peptide families were identified. Among these, we report the occurrence of two phyllokinins, and one medusin-SP which were previously reported in other related species. In addition, eight novel peptides were identified, including four dermaseptins, DRS-SP2 to DRS-SP5, one phylloseptin-SP1, and three orphan peptides. Phylloseptin-SP1 and dermaseptins-SP2 were identified in HPLC fractions based on their molecular masses determined by MALDI-TOF MS. Among the antimicrobial peptides, dermaseptin-SP2 was the most potent, inhibiting Escherichia coli, Staphylococcus aureus, and ORSA with a minimum inhibitory concentration (MIC) of 2.68 μM, and Candida albicans with an MIC of 10.71 μM, without haemolytic effects. The peptides described in this study represent but a superficial glance at the considerable structural diversity of bioactive peptides produced in the skin secretion of A. spurrelli.

Background The combination of classical cytogenetics with molecular techniques represents a powerful approach for the comparative analysis of the genome, providing data for the systematic identification of chromosomal homologies among species and insights into patterns of chromosomal evolution within phylogenetically related groups. Here, we present cytogenetic data on four species of Neotropical treefrogs of the genus Phyllomedusa ( P. vaillantii , P. tarsius , P. distincta , and P. bahiana ), collected in Brazil and Ecuador, with the aim of contributing to the understanding of the chromosomal diversification of this genus. Results With the exception of P. tarsius , which presented three telocentric pairs, all the species analyzed had conservative karyotypic features. Heterochromatic patterns in the genomes of these species revealed by C-banding and fluorochrome staining indicated the presence of a large number of non-centromeric blocks. Using the Ag-NOR method and FISH with an rDNA 28S probe, we detected NOR in the pericentromeric region of the short arm of pair 7 in P. vaillantii , pair 1 in P. tarsius , chromosomes 1 and 9 in P. distincta , and in chromosome 9 in P. bahiana , in addition to the presence of NOR in one homologue of chromosome pair 10 in some individuals of this species. As expected, the telomeric probe detected the terminal regions of the chromosomes of these four species, although it also detected Interstitial Telomeric Sequences (ITS) in some chromosomes of the P. vaillantii , P. distincta and P. bahiana karyotypes. Conclusion A number of conservative chromosomal structures permitted the recognition of karyotypic homologies. The data indicate that the presence of a NOR-bearing chromosome in pair 9 is the plesiomorphic condition in the P. burmeisteri group. The interspecific and intraspecific variation in the number and location of rDNA sites reflects the rapid rate of evolution of this character in Phyllomedusa . The ITS detected in this study does not appear to be a remnant of structural chromosome rearrangements. Telomeric repeats were frequently found in association with heterochromatin regions, primarily in the centromeres, which suggests that (TTAGGG)n repeats might be an important component of this heterochromatin. We propose that the ITSs originated independently during the chromosomal evolution of these species and may provide important insights into the role of these repeats in vertebrate karyotype diversification.

Antimicrobial peptides (AMPs) constitute part of a broad range of bioactive compounds present on diverse organisms, including frogs. Peptides, produced in the granular glands of amphibian skin, constitute a component of their innate immune response, providing protection against pathogenic microorganisms. In this work, two novel cruzioseptins peptides, cruzioseptin-16 and -17, extracted from the splendid leaf frog Cruziohyla calcarifer are presented. These peptides were identified using molecular cloning and tandem mass spectrometry. Later, peptides were synthetized using solid-phase peptide synthesis, and their minimal inhibitory concentration and haemolytic activity were tested. Furthermore, these two cruzioseptins plus three previously reported (CZS-1, CZS-2, CZS-3) were computationally characterized. Results show that cruzioseptins are 21–23 residues long alpha helical cationic peptides, with antimicrobial activity against E. coli, S. aureus, and C. albicans and low haemolytic effect. Docking results agree with the principal action mechanism of cationic AMPs that goes through cell membrane disruption due to electrostatic interactions between cationic residues in the cruzioseptins and negative phosphate groups in the pathogen cell membrane. An action mechanism through enzymes inhibition was also tried, but no conclusive results about this mechanism were obtained.

In this research, we present a preliminary computational study of four Dermaseptin-related peptides from the skin exudate of the gliding tree frog Agalychnis spurrelli . Experimentally, the amino acid sequence of these peptides was elucidated through molecular cloning and tandem mass spectrometry and synthetic peptides were assayed against E. coli , S. aureus , and C. albicans to determine their antimicrobial properties. With the sequences on hand, a computational study of the structures was carried out, obtaining their physicochemical properties, secondary structure, and their similarity to other known peptides. A molecular docking study of these peptides was also performed against cell membrane and several enzymes are known to be vital for the organisms. Results showed that Dermaseptin-related peptides are α-helical cationic peptides with an isoelectric point above 9.70 and a positive charge of physiological pH. Introducing theses peptides in a database, it was determined that their identity compared with known peptides range from 36 to 82% meaning these four Dermaseptins are novel peptides. This preliminary study of molecular docking suggests the mechanism of action of this peptide is not given by the inhibition of essential enzymatic pathways, but by cell lysis. Graphical abstract

Fil: Boeris, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentina. Universidad Nacional de Misiones; Argentina