Hafizeh Haghighatafshar - Department of Microbiology, Urmia Branch, Islamic Azad University, Urmia, Iran
Reza Talebi - Department of Microbiology, Faculty of Basic Science, Urmia Islamic Azad University, Urmia, Iran
Amir Tukrmechi - Department of Pathobiology and Quality Control, Artemia and Aquatic Animals Research Institute, Urmia University, Urmia, Iran

Background: Bacteriocins are heterogeneous inhibitory substances that could affect the bacteria belonging tothe same genus. Both gram-positive and gram-negative bacteria produce bacteriocins. One of the best sourcesof producing bacteriocins is Lactobacillus. The aim of this study was to isolate and purify bacteriocin fromLactobacillus rhamnosus and assess its effects on Pseudomonas aeruginosa and synthesis of its lipopolysaccharide.Methods: L. rhamnosus was prepared and cultured at MRS broth and incubated at ۳۷ºC for ۲۴ hours. Then, themedium was centrifuged for the isolation of bacteriocin and the supernatant was considered as bacteriocin.Antibacterial properties of different concentrations of bacteriocin (۵۰, ۱۰۰, ۲۰۰, and ۴۰۰ μg/mL) against P.aeruginosa were assayed by using agar diffusion and broth micro dilution methods. Also, the effect of bacteriocinagainst lipopolysaccharide synthesis in P. aeruginosa was analyzed by using one unit of minimum inhibitoryconcentration (MIC) for bacteriocin.Results: The results showed that all bacteriocin concentrations had antibacterial activity against P. aeruginosa.The MIC value was ۳۱.۲۵ μg/mL and minimal bactericidal concentration (MBC) was ۶۲.۵ μg/mL. Also, thesynthesis of lipopolysaccharide decreased during P. aeruginosa growth period, and it reached zero after ۵ hours.Conclusions: The results of this study showed the antibacterial effect of bacteriocin isolated from L. rhamnosusagainst P. aeruginosa. In addition, this bacteriocin prevented the lipopolysaccharide synthesis in P. aeruginosa.

Bacteriocin, Lactobacillus rhamnosus, Lipopolysaccharide, Pseudomonas aeruginosa