ANTIMICROBIAL MODE OF ACTION OF SECRETIONS FROM THE METAPLEURAL GLANDOF MYRMECIA-GULOSA (AUSTRALIAN BULL ANT)

Secretions from exocrine metapleural glands of Myrmecia gulosa (Austra lian bull ant) exhibit broad-spectrum antimicrobial activity. Treatmen t of the yeast Candida albicans with metapleural secretion resulted in the rapid and total leakage of K+ ions from cells within 10 min. Ultr astructural analysis of the bacteria Bacillus cereus, Escherichia coli , and Pseudomonas aeruginosa, and cells and protoplasts of Candida alb icans demonstrated gross damage of the cell membrane and aggregation o f the cytoplasmic matrix of treated cells. Degradation of membrane-bou nd organelles was also observed in Candida albicans. The antimicrobial ly active components of metapleural secretions were nonpolar and inter acted with the phospholipid bilayer, causing damage to the structural integrity of liposomes and the release of carboxyfluorescein. The data suggest that the antimicrobial agents in metapleural secretion act pr imarily by disrupting the structure and function of the phospholipid b ilayer of the cytoplasmic membrane.