Bacitracin is a cyclic polypeptide antibiotic isolated from Bacillus subtilis. It is made up of a variety of antimicrobial peptide fractions including A, A1, B, B1, B2, C, D, E, F, G, and X. This standard grade product is a mixture of these fractions, with bacitracin A exhibiting the most potent antimicrobial activity. Bacitracins B1 and B2 exhibit about 90% of the antimicrobial activity of bacitracin A when together. Other forms of bacitracin have not been studied extensively, but may have negligible antimicrobial properties. Bacitracin is freely soluble in aqueous solution.