Anti-biofilm and anti-bacterial effects of bacteriocin-producing strains of Escherichia coli and Bacillus subtilis

The prevalence of infection, along with the spread of antibiotic-resistant bacteria has caused the antibacterial peptide, bacteriocins, to be considered. The purpose of this study was to compare the antibacterial effect of bacteriocin-producing bacteria. The inhibitory activity of bacteria isolated from different regions of Semnan soil, Dasht Desert (Semnan University Bacterial Culture Collection; DDBCC) was studied against the indicators by agar diffusion method. Candidate strains were identified by biochemical and molecular tests. Concentrating the selected bacteriocins by ammonium sulfate saturation, the effects of biofilm destruction were studied. Then, using a thin layer chromatography the selected bacteriocins were purified and their antimicrobial activity was confirmed. The 16s rRNA sequencing results showed 98% similarity of DDBCC38 and DDBCC51 isolates to E. coli and 96% similarity of the DDBCC46 isolate to Bacillus subtilis. Concentrated DDBCC51 and DDBCC38 bacteriocins inhibited the growth of Bacillus cereus, Bacillus anthracis, and Klebsiella pneumonia after 52 hours. Pseudomonas aeruginosa and Staphylococcus aureus biofilms were destructed by DDBCC51 and DDBCC38 bacteriocins 12.0% and 40.0%, and 19.6% and 40%, respectively. In contrast, concentrated DDBCC46 bacteriocin was effective on K. pneumonia and P. aeruginosa in 72 hours but had no effect on biofilm destruction. The purification of DDBCC38 and DDBCC51 bacteriocins by thin layer chromatography resulted in 2 mm increasing of inhibition zone diameter against K. pneumoniae. However, purified DDBCC46 bacteriocin reduced it by 4 mm. Considering the anti-biofilm and antagonistic properties of the respective isolates, further studies for optimization of the production conditions and molecular identification of the produced
bacteriocin are proposed