Preparation and properties of antimicrobial peptides from skin secretion of Bufo melanostictus

The skin secretion of Bufo melanostictus was collected and purified by separate proteins on a Sephadex G-25 column.Antimicrobial activity was determined by miniaturized methods.Antibacterial activities against the Gram positive bacteria Staphylococcus aureus and Bacillus subtilis,and the gram negative bacteria Aeromonas hydrophial were obserbed.Weak antibacterial activity for the gram negative bacteria V.alginolyticus,V.parahaemolyticus,V.fluvialis and Escherichia coli were also observed.The skin secretion of Bufo melanostictus had no antibacterial activity when it was digested with a proteinase trypsin.The result indicated that the antibacterial component was a protein.The peptides cultured at various water temperature and pH showed antimicrobial stability against the temperature and pH.It was no hemolysis for fish red blood cells on the low concentration.