IDENTIFICATION OF BACTERIOCIN GENES IN PROBIOTIC STRAINS OF LACTIC ACID BACTERIA LACTOBACLLUS ACIDOPHILUS D-75 AND LACTOBACILLUS ACIDOPHILUS D-76.

Aim: to detect the bacteriocin genes of probiotic strains Lactobacillus acidophilus 0-75 and Lactobacillus acidophilus D-76 (components of Vitaflor dietary supplement).

Materials and methods: The antagonistic activity of L. acidophilus D-75 and L. acidophilus D-76 strains was estimated by the deferred antagonism method. The identification of bacteriocin genes was performed by PCR using helveticin J gene primers. Amplified fragments were sequenced using ABI PRISM' 310 Genetic Analyzer and were analyzed using NCBI/BLASTX.

Results: The test bacteria exhibit pronounced antagonistic activity (AA) against Escherichia coli 075 and Salmonella Enteritidis 209. In the presence of Actoflor-S (metabiotic dietary supplement) the antagonistic activity of tested probiotic strains was 2-2.5-fold increased indicating its inducible nature. The identical sequences of 537 bp homologous to gene fragment of helveticin of L helveticus DPC457l (hv_1632 gene) were detected in DNA of both strains. Sequencing of these fragments showed difference in three nucleotides.compared to the reference DNA of DPC4571 strain (A instead of G at position 46, C instead of T at position .249 and A instead of T at position 537), but all these replacements do not lead to changes in the amino acid sequence of a bacteriocin. For L acidophilus D-76 another bacteriocin gene fragment of 283 bp was identified (in addition to 537 bp fragment). The latter had 95% homology with the helveticin J gene of L helveticus R0052 (R0052_09025 . gene). In NCBI/BLASTX database the sequences homologous to the helveticin gene of L. helveticus DPC4571 were found in 11 microorganisms related to L. acidophilus, L. amylovorus, L. crispaus, L gallinarum, L. helveticus and L. kitasatonis.

Conclusion: Thus, our study shows that there are at least two bacteriocins in L. acidophilus D-76 and one bacteriocin in L. acidophilus D-75. However, the true potential of these probiotic bacteriocins for human health has yet to be releized.