Figure 1.
Comparison of bacteriocin production at different phases of growth curve.
The growth curve analysis of strain Brevibacillus sp. GI-9 indicates that the production of bacteriocin initiated at late logarithmic phase. Growth measured as absorption at 600 nm is indicated by squares (left y axes), while the bacteriocin activity by triangles (right y axes).
Figure 2.
Gel filtration elution profile of laterosporulin (A) and analysis (B).
(A) The major peak (highlighted fraction) in gel filtration chromatography shows antimicrobial activity and the calibration curve obtained from protein standards indicates mass of the peptide in the range of 5.3 to 10.1 kDa. (B) Tricine-SDS-PAGE analysis of the major peak showed a single band; lane 1, molecular weight markers; lane 2, purified laterosporulin.
Figure 3.
MALDI-TOF mass spectrometry analysis of laterosporulin.
The purified bacteriocin from Brevibacillus sp. GI-9 shows the mass (m/z) of 5.6 kDa.
Figure 4.
Determination of MIC for laterosporulin produced by strain GI-9.
The MIC assay for Gram-positive and Gram-negative bacteria with purified laterosporulin using micro-titer plates in triplicates revealed that B.subtilis and S. aureus are highly sensitive.
Figure 5.
Bactericidal effect of laterosporulin on E. coli.
The scanning electron micrographs of E. coli cells without laterosporulin treatment (A) and after laterosporulin treatment (500 µg/ml) for 4 h (B). Note that the treatment of E. coli displaying roughening of cell surface with cell debris as a result of treatment.
Figure 6.
Genetic organization of 4 kb region of the genome encoding laterosporulin (A) and nucleotide sequence of the ORF (B).
The putative ORF encoding laterosporulin structural gene is shown by filled arrow and flanking ORFs as shown by empty arrows (A). Panel B shows the nucleotide sequence of the laterosporulin gene (encoding the indicated amino acids) with putative start codan, stop codons and ribosome binding site (RBS) shown in bold.