Antimicrobial activity of snake β-defensins and derived peptides

β-defensins are antimicrobial peptides presenting in vertebrate animals. They participate in innate immunity, but little is known about them in reptiles, including snakes. Although several β-defensin genes were described in Brazilian snakes, their function is still unknown. The peptide sequence from these genes was deduced, and synthetic peptides (with approximately 40 amino acids and derived peptides) were tested against pathogenic bacteria and fungi using microbroth dilution assays. The linear peptides, derived from β-defensins, were designed applying the bioisosterism strategy. The linear β-defensins were more active against Escherichia coli, Micrococcus luteus, Citrobacter freundii, and Staphylococcus aureus. The derived peptides (7–14 mer) showed antibacterial activity against those bacteria and on Klebsiella pneumoniae. Nonetheless, they did not present activity against Candida albicans, Cryptococcus neoformans, Trychophyton rubrum, and Aspergillus fumigatus showing that the cysteine substitution to serine is deleterious to antifungal properties. Tryptophan residue showed to be necessary to improve antibacterial activity. Even though the studied snake β-defensins do not have high antimicrobial activity, they proved to be attractive as template molecules for the development of antibiotics.

Antimicrobial Activity of Snake ß-Defensins and Derived Peptides.

ß-defensins are antimicrobial peptides presenting in vertebrate animals. They participate in innate immunity, but little is known about them in reptiles, including snakes. Although several ß-defensin genes were described in Brazilian snakes, their function is still unknown. The peptide sequence from these genes was deduced, and synthetic peptides (with approximately 40 amino acids and derived peptides) were tested against pathogenic bacteria and fungi using microbroth dilution assays. The linear peptides, derived from ß-defensins, were designed applying the bioisosterism strategy. The linear ß-defensins were more active against Escherichia coli, Micrococcus luteus, Citrobacter freundii, and Staphylococcus aureus. The derived peptides (7-14 mer) showed antibacterial activity against those bacteria and on Klebsiella pneumoniae. Nonetheless, they did not present activity against Candida albicans, Cryptococcus neoformans, Trychophyton rubrum, and Aspergillus fumigatus showing that the cysteine substitution to serine is deleterious to antifungal properties. Tryptophan residue showed to be necessary to improve antibacterial activity. Even though the studied snake ß-defensins do not have high antimicrobial activity, they proved to be attractive as template molecules for the development of antibiotics.

The relationship of cell cycle phases and embryonic development of Bothrops snakes

Squamatas are the only strain of reptiles with species that give birth to free- living neonates (viviparity), capable of living independently of extraembryonic tissues. In many Viperidae species reproduction is seasonal, but not all females reproduce in a given year. Intra and interspecific variations also occur in relation to mating and follicular activity, thus allowing hormonal changes responsible for physiological events. The routine deposit of infertile and abnormal eggs in both oviparous and viviparous Squamata species is routinely reported. Follicular atresia is a hormonally controlled degenerative process by which ovarian follicles, at various stages of development and growth, of mammalian and non- mammalian vertebrates lose their integrity and are eliminated before ovulation. Apoptosis, a fundamental mechanism for germinal cell removal, a highly regulated and highly efficient cell death program. In order to monitor and investigate the high number of atretic eggs released by captive Bothrops snakes, we investigated possible apoptotic cell death studing cell cycle as a molecular approaches. Different cell cycle phases were identified in the embryos of captive Bothrops snakes. In Gate-1 the cells were mostly in division (Mitosis) than Gate-2. In both gates the cells are in phase S, synthesizing proteins and DNA to divide. The atretic eggs showed different stages of development, differentiation and maturation, and that cells were involved in the organogenesis of these snake species. The hypothesis from: "Is atretic egg fertilized?" to atretic egg. In this study was confirmed by the identification of germinal disks in different stages of organogenesis, which expressed different stages of growth kinetics and cell differentiation. Oxidative stress can modulate cell development in cell division leading to cell fragmentation and cell death.

Beta-defensin genes of the Colubridae snakes Phalotris mertensi, Thamnodynastes hypoconia, and T. strigatus

beta-Defensins are cationic antimicrobial peptides showing little sequence similarity but highly conserved tertiary structure stabilized by a six-cysteines-motif. Using a PCR approach, we described beta-defensin sequences with two exons in three species of Colubridae snakes with high sequence similarity between them. The deduced amino acid sequence presented the characteristics of beta-defensin family. The phylogenetic analysis using beta-defensin coding sequences of different snakes grouped them in two main branches: genes organized in three or two exons.