Bacitracin is a polypeptide antibiotic recovered from certain strains of B. spizizenii (former B. subtilis) and B. licheniformis. It inhibits cell wall biosynthesis in gram-positive bacteria and Neisseria by inhibition of peptidoglycan synthesis. Bacitracin may as well be used as protease inhibitor.
Min. 60 000 IU/g. Main component Bacitracin A. Bactericidal activity requires divalent cations like Zn²⁺ (1). The concentration of stock solution is 100 - 1000 mg/ml in H₂O or ethanol, stored at -20 °C. The working concentration is 0.1 - 1 mg/ml (0.07 - 0.7 mM). Bacitracin is very stable in a pH range of 4 - 5, but is rapidly inactivated in pH of over 5 at room temperature.

1. Scogin, D. et al. (1980) Biochemistry 19, 3348-52