MALDI-TOF-MS analysis of P. polymyxa M-1 secondary metabolites. (A) Culture supernatant of M-1 grown in GSC medium containing fusaricidin (series 1, from m/z = 883.1 to 983.5) and polymyxin P (series 2, from m/z = 1177.9 to 1267.9) derived mass peaks. (B) Extended view of the mass peaks m/z forming series 2. Two polymyxin P metabolites [M + H]+m/z 1177.9 and 1191.9, and their alkali adducts [M + Na]+m/z 1199.9 and 1213.9, [M + K]+m/z 1229.9, and [M-H + 2 K]+m/z 1253.9 and 1267.9 were distinguished. The nature of the trailing peaks next to the peaks of interest is unknown.