Tracing of IIa and IIb bacteriocins in native strains of Lactobacillus isolated from traditional dairy products

Lactic acid bacteria produce bacteriocin as antibacterial protein molecules with diverse genetic origins. Therefore, identifying the bacteriocin class of native lactic acid bacteria could lead to an understanding of the antibacterial function of these peptides. In this study, presence of two subgroup of bacteriocins (IIa and IIb) in native strain of Lactic acid bacteria was investigated. After screening of this strains against two Index microorganisms including Listeria innocua (ATCC 33090), and Escherichia coli (ATCC 1399) by disk diffusion assay, the five strains with highest diameter of growth inhibitory against these index pathogens was selected. The molecular weight of peptides secreted by lactic acid bacteria was estimated by ammonium sulfate precipitation. Upstream and downstream sequences of the bacteriocin structural gene were used to identify bacteriocin-producing lactic isolates in the polymerase chain reaction. The results of SDS - PAGE showed bands with a molecular weight of less than 10 kDa for these strains. Sequencing of the polymerase chain reaction product led to the identification of plnN, plnJK and plnEF gene regions in N isolate and plnJK and plnEF gene regions in M isolate. Therefore, isolates M and N have good potential for use in increasing the quality level of dairy products and animal feed. The multalign results of sequences showed showed that the native strains in Iran are very similar (99%) with Lactobacillus plantarum FQ and ATCC BAA-793 strains. Inhibitory effects against foodborne pathogens can be used if additional experiments are performed to isolate present bacteriocins in M and N native strains.