Tyrocidine complex is a mixture of cyclic decapeptides originally isolated from B. brevis. It can be composed of 4 different amino acid sequences, giving tyrocidine A–D. Tyrocidine was the first commercially available antibiotic, but has been found to be toxic toward human blood and reproductive cells. The function of tyrocidine within its host B. brevis is thought to be regulation of sporulation.

[1] Juhl DW, van Rensburg W, Bossis X, Vosloo JA, Rautenbach M, Bechinger B. Tyrocidine A interactions with saccharides investigated by CD and NMR spectroscopies. J Pept Sci. 2019 May;25(5):e3163.

[2] "Antibiotics". The Columbia Electronic Encyclopedia. 6th ed. Columbia University Press. 2007. pp. online.

[3] Roskoski R, Gevers W, Kleinkauf H, Lipmann F (December 1970). "Tyrocidine biosynthesis by three complementary fractions from Bacillus brevis (ATCC 8185)". Biochemistry. 9 (25): 4839–45. doi:10.1021/bi00827a002. PMID 4320358.