Production of the Novel Two-Peptide Lantibiotic Lichenicidin by Bacillus licheniformis DSM 13
Figure 6
MALDI-TOF mass spectra of the B. licheniformis MW3 wild type (A) and its insertion mutans LicM1INT (B) and LicM2INT (C).
The isopropanol extracts of the insertion mutants B. licheniformis LicM1INT and LicM2INT were characterized by the loss of activity against M. luteus. MALDI-TOF spectra of these isopropanol extracts in comparison to the wildtype (A) showed the loss of a peak at 3251 Da in the case of the LicM1 insertion mutant (B) indicating that this peak represents the protonated form of the active Licα peptide. The insertion of a plasmid into the gene of the modification enzyme LicM2 inactivated this enzyme and most probably exerted a polar effect on the downstream genes, thus affecting production of both peptides. This mutant did not produce the Licα peptide and is further characterized by the absence of a 3021 Da peak, which might represent the protonated form of the mature Licβ peptide, harboring 12 dehydrated residues (C). In some cultivations a further peak of 3039 Da was observed, which probably denotes a Licβ peptide with only 11 of 15 possible dehydrations.