Figure 4

MALDI-TOF mass spectrum of bacteriocin-like peptide (A) and lipopeptide (B) obtained by solvent extraction. Spectrum was acquired in positive ion linear mode and reproducibility of the spectrum checked several times with different spots of same sample. (C) Scanning electron micrograph of S. aureus MTCC1430 cells (I) without treatment of bacteriocin-like peptide and (II) after treatment with bacteriocin-like peptide (6.0 μM) for 4 h. (D) Antibacterial activity of the peptides using well diffusion assay. After each peptide was serially diluted 100 μl of the lowest dilution inhibiting test strain were used for bacteriocin-like peptide (B), lipopeptide (L) and 50 μl of same dilutions were used to check the combined effect (B+L) on L. monocytogenes (I) and M. luteus (II). The bacteriocin-like peptide showed 14 and 12 mm inhibition zone for L. monocytogenes and M. luteus respectively. Lipopeptide yielded 11 mm zone for both strains. However, additive effect of both peptides showed a zone of 17 and 15 mm for L. monocytogenes and M. luteus respectively. Similar results were obtained in three individual experiments.