Bacitracin and Gramicidin

Bacitracin was first isolated in 1943 from a strain of Bacillus spp. that was originally classified as Bacillus subtilis (Johnson et al., 1945) but is now known as Bacillus licheniformis (Katz and Demain, 1977). The molecular formula is C₆₆H₁₀₃N₁₇O₁₆S (Figure 83.1), and it has a molecular weight of 1422.7. Bacitracin consists of a mixture of related nonribosomally synthesized cyclic metallopolypeptides (bacitracin A, B, and C and several minor components), and variations in molecular weight have been described. Bacitracin A is the main component of bacitracin preparations (Stone and Strominger, 1971). It has a bactericidal effect on most Gram-positive bacteria owing to its interference with bacterial cell wall formation. In humans, bacitracin’s toxicity mainly restricts its application to topical use. Bacitracin was (and sometimes still is) used as growth promoter in animal husbandry. Figure 83.1 Structure of bacitracin. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315152110/08d8042d-9481-4a8d-8c27-9bd589f6de6b/content/fig83_1.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>