It seems like the sea is proving to be a mine for anitmicrobial peptides (see previous entries on compounds from Fijian seaweeds and furanones). This time, researchers from the North Carolina Sea Grant have isolated "American oyster defensin" (AOD), an antimicrobial peptide purified from acidified gill extract of the American oyster (Crassostrea virginica) using acid-urea--PAGE and reversed-phase HPLC.

The 4265.0 Da peptide had 38 amino acids, including 6 cysteines. It showed strongest activity against Gram-positive bacteria (Lactococcus lactis subsp. lactis and Staphylococcus aureus, but also had significant activity against Gram-negative bacteria (Escherichia coli D31 and Vibrio parahemolyticus.

The findings are published in the Biochemical and Biophysical Research Communications (abstract; full-text available upon subscription).