Nature of the Bactericidal Action of Antimycin a for Bacillus Megaterium.

Marquis, Robert E. (University of Rochester, Rochester, N.Y.). Nature of the bactericidal action of antimycin A for Bacillus megaterium. J. Bacteriol. 89:1453-1459. 1965.-Antimycin A, a fungicidal antibiotic which specifically inhibits metabolic reduction of cytochrome c, was found to be lethal for Bacillus megaterium. However, the bactericidal action was correlated with a capacity of antimycin to hinder plasma-membrane functions other than cytochrome-mediated respiration. With conditions under which oxygen consumption was not appreciably depressed, antimycin almost completely inhibited concentrative uptake of both alpha-aminoisobutyrate and alpha-methylglucoside, and also caused death of cells. When present in amounts greater than those required for killing or for inhibition of nutrilite uptake, antimycin also induced extensive loss of inorganic phosphate and other substances from whole cells, inhibited aerobic respiration, and acted as a lytic agent for isolated protoplasts. The lytic potency of antimycin was greater, on a molar basis, than that of digitonin, hexachlorophene, polymyxin B, and all but one of a number of test detergents. Protoplasts concentrated antimycin primarily in or on the plasma membrane, and the refractive index of isolated protoplast membranes rose sharply as a result of antimycin binding. In all, antimycin-induced lysis appeared not to include dissolution of the protoplast membrane similar to that produced by dodecyl sulfate. Rather, the lytic process seemed more akin to that induced by cationic detergents or by polymyxin.