Mode of action of iturin A, an antibiotic isolated from Bacillus subtilis, on Micrococcus luteus.

Iturin A has an antibacterial activity on M. luteus which is strongly reduced in presence of MgCl₂. Iturin A lyses M. luteus protoplast, this lysis is enhanced by EDTA and inhibited by MgCl₂. These results suggest an action of iturin A on cytoplasmic membrane with interactions of both lipophilic and polypeptidic moieties of the antibiotic, respectively with membrane lipids and membrane polar components. Polar interactions involve the participation of mineral ions as magnesium ions have a strong inhibition effect on the activity of iturin A. The effect of iturin A on the incorporation of radio-active thymidine, uracil, isoleucine and alanine seems unspecific and is probably a consequence of the primary action on cytoplasmic membrane.