Studies on a Strain of Bacillus brevis Isolated from Soil : Part II. Purification of Antibiotics and their Characteristics

Two kinds of antibiotics were harvested from a strain recently isolated. The supernatant of the culture at 28℃ showed a broad spectrum against Gram-positive and -negative bacteria. However, the supernatant of the culture at 37℃ showed growth inhibition only against Gram-positive bacteria. These substances were separated and purified through the successive steps involving column chromatography using Amberlite CG-50 and Sephadex G-25. These two antibiotics were identified as Gramicidin S and Polymyxin A. Furthermore, it was shown that these two antibiotics were simultaneously produced at 28℃. Gramicidin S was also produced at temperatures up to 40℃, however, Polymyxin A was not above 35℃. Two mutants lacking of polymyxin producing ability were obtained from the strain by acriflavin treatment.