Isolation and characterization of peptide antibiotics LI-F04 and polymyxin B6 produced by Paenibacillus polymyxa strain JSa-9.

Paenibacillus polymyxa JSa-9 had been found to produce five cyclic LI-F type antibiotics which were released into culture medium in accordance with our previous report. In this study, another three kinds of antagonistic compounds were extracted from P. polymyxa JSa-9 cell pellets and (or) spores by methanol. Using high performance liquid chromatography (HPLC) method, two antagonistic fractions were separated and collected from the methanol extract. One showed inhibition against Escherichia coli and Staphylococcus aureus, while the other was active against Aspergillus niger and S. aureus. By means of electrospray ionization mass spectroscopy (ESI-MS), infrared spectroscopy (IR), and amino acid analysis, two kinds of compounds from fraction B with molecular masses of 901 and 915Da were characterized as the linear lipopeptide analogs of antibiotics LI-F04a and LI-F04b, respectively. Another antimicrobial substance from fraction A could be attributed to polymyxin B(6).