ANTISEPTICS of biological origin are now well known since the pioneer investigations of Fleming on penicillin and Dubos on tyrothricin. In our laboratory early in 1942 an attempt was made to isolate the strains of Bacillus brevis from Russian soils in order to prepare tyrothricin similar to that of Dubos. In the course of this work we isolated from soil a new strain of aerobic sporulating bacillus possessing some unique characteristics. It is well known that alcoholic extract of the acid precipitate of the culture of B. brevis contains an amorphous body, designated by Dubos and Hotchkiss (1941) as tyrothricin, which can be afterwards fractionated by special procedures into two individual crystalline substances, gramicidin and tyrocidine hydrochloride. In distinction from this, alcoholic extract of the acid precipitate from our strain consists almost entirely of the antibacterial substance, which is not amorphous but is directly crystallizable from the alcoholic solution. This crystalline substance can be further purified and obtained in the form of colourless needles with the melting point 267–268°. Hence it is different from gramicidin (m.p. 228–230°) and tyrocidine hydrochloride (m.p. about 240°). The bacteria producing this substance were designated as the strain of Gause-Brazhnikova, and the substance itself as gramicidin S (Soviet gramicidin).
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