Boromycin, at a concentration of 0.05 μg/ml inhibits the synthesis of protein, RNA and DNA in whole cells of Bacillus subtilis. It is being antagonised by surface active compounds and is being bound to lipoprotein. Binding of the boromycin within the cell especially takes place at the cytoplasmic membrane. The inhibitory effect to Bacillus subtilis is being reversed by high concentration of potassium salts (e.g. 0.2 m KCl). The reversion is specific of potassium salts. After the adding of boromycin a discharge of potassium ions from the cells can be observed. The K+-Na+-activated ATP-ase of the cytoplasmic membrane is not influenced by boromycin. On an artificial membrane of carbon tetrachloride boromycin shows a low selectivity for potassium ions compared with sodium and lithium ions. The degradation of boromycin through alkaline and acid hydrolysis leads to a loss of antibiotic activity, due to the splitting off the boric acid from the molecule. © 1969 Springer-Verlag.
