The Chemical Nature of Gramicidin and Tyrocidine

The work reported here is a continuation of earlier investigations on the chemical nature of two bactericidal substances, gramicidin and tyrocidine, isolated from cultures of Bacillus brevis (1-3). Christensen, Edwards, and Piersma are at the same time submitting a report of work which has been carried on independently in their laboratory (4). Tyrocidine hydrochloride and gramicidin are both colorless crystalline substances, soluble in organic solvents and optically active. Their biological properties offer certain interesting contrasts (1, 5). Gramicidin appears to be more specific in its antibacterial action and to retain this property to a greater extent in the presence of animal tissue. Accordingly, the study of its chemical nature has been pursued more actively than that of tyrocidine.