Further studies on the lethal effect of long-chain fatty acids on mycobacteria

Mycobactericidal activity of long-chain fatty acids was confirmed by in vitro exposure of BCG. The killing effect was accompanied by inhibition of the membrane-bound acid phosphatase activity. Such active fatty acids were those having a stronger hemolytic activity (e.g., C12:0, C14:0, C18:1, C18:2). Heat-killed BCG cells or their cell walls adsorbed the toxic fatty acids, whereas the fatty acid-insensitive E. coli cells did not. It was suggested that the mycobactericidal action of long-chain fatty acids is due to their detergent-like action on the cytoplasmic membrane, and that the determinant factor for the fatty acid-sensitivitiy of bacteria is the property of the cell wall by which fatty acids are adsorbed so that the active site is brought into contact with the inner membrane.