| Antimicrobial peptides (AMPs) are important resources from which it may be possible to develop novel therapeutic agents against the ever growing number of antibiotic resistant microorganisms. The red-backed salamander, Plethodon cinereus, may possess one or more AMPs which could be developed as excellent therapeutic agents. In addition, the characterization of salamander AMPs could provide illumination on the mechanism of action of AMPs in general.; Environmental health has indirect effects on human as well as animal health. P. cinereus may make a good, terrestrial ecological indicator throughout the Appalachian mountains. For this to happen, a correlation must be made between the health of P. cinereus and the health of their environment. AMPs are part of the innate immune system and could be used to assess the health status of P. cinereus.; One antimicrobial peptide was isolated and partially characterized from the skin of P. cinereus. The isolation included the use of cation-exchange chromatography and reverse-phase high performance liquid chromatography. The various compounds (fractions) obtained were tested against two strains of the Gram-negative bacterium Escherichia coli and the Gram-positive bacterium, Staphylococcus aureus. No fractions showed significant activity against E. coli. The fraction showing the greatest activity against S. aureus underwent further characterization and was named plethodin.; The molecular weight of plethodin was estimated using both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry. The molecular weight of plethodin was estimated to be 13,750 daltons. Plethodin was shown to have no disulfide bridges and to be heat stable. An analysis of the molar percent of each amino acid was performed and a partial amino acid sequence was revealed to be: N-terminus-XXXTGDGDLNLGEXLK.; Plethodin was active against Staphylococcus epidermidis and the yeast, Saccharomyces cerevisiae, but not against two other Gram-positive bacteria, Enterococcus faecalis or Bacillus cereus, or the pathogenic yeast, Candida albicans . Several assays suggested that the mechanism of action did not involve damage to the cell wall of or a direct effect on oxidative phosphorylation in S. aureus. Plethodin appears to inhibit the growth of the bacteria rather than killing them, producing a bacteriostatic effect. |
