Bacteriolytic cell-free fluid of culture filtrates of actinomycetes. Produced by most species of Streptomyces; studied mostly in Streptomyces albus. Protein-like in nature. Stated to consist of a bactericidal fatty acid fraction and an enzyme: Welsch, J. Bacteriol. 42, 801 (1941); 44, 571 (1942); 53, 101 (1947). Dissolves dead gram-negative, and, with more difficulty, dead gram-positive organisms. Also dissolves living organisms in aq suspensions, such as Staph. aureus. In answer to the question whether actinomycetin deserves the name “antibiotic”, see the polemic between Hoogerheide and Welsch, Bot. Rev. 10, 599 (1944) and J. Bacteriol. 53, 101 (1947). Purification and prepn from Streptomyces albus: Ghuysen, BE 517191 and BE 521114 (both 1953 to Soc. Belge de l'Azote), C.A. 53, 5600g, 12593e (1959). Review: Caltrider in Antibiotics vol. 1, D. Gottlieb, P. D. Shaw, Eds. (Springer Verlag, New York, 1967) pp 681-683.