Tracking, sequencing and structural investigation of the genes encoding toxins of the lacticin family (Lactococcus lactis) in bacterial samples isolated from whey and investigating the effect of the toxin produced on the MCF۷ cell line.

BACKGROUND AND OBJECTIVESOne of the biggest health challenges of human societies is the resistance of prokaryotic and eukaryotic cells to drugs. The use of probiotics and bacterial toxins, which can meet therapeutic goals with high specificity and very low side effects, is progressing day by day. Therefore, the aim of this study is to track, sequence and structurally investigate the genes encoding lacticin family toxins in bacterial samples isolated from whey and investigate the effect of the toxin produced on the MCF۷ cell line.MATERIALS AND METHODSIn this method, different whey samples were prepared and cultured using MRS medium at ۳۷ degrees Celsius. The isolated bacteria were examined using biochemical tests and the isolates that were most similar to Lactococcus lactis were selected. Then the presence of lacticin gene was checked by PCR colony. In the next step, two isolates that had lacticin gene were selected and the effect of bacteriocin produced by them on Staphylococcus aureus bacteria was studied by well-plate method. Next, purified lacticin using dialysis bag was analyzed by SDS-PAGE and Bradford. The strain with the highest lacticin production was identified by sanger sequencing. Finally, the effects of lacticin obtained from this strain was studied on MCF-۷ breast cancer cell line using MTT and scratching method.RESULTS AND DISCUSSIONThe results of this study determined that the selected bacterium containing the lacticin producing gene is Lactococcus lactis, which was registered in the NCBI database with the accession number OQ۳۸۳۹۲۹. The growth of this bacterium in acidic conditions (pH=۲.۵) did not show a significant difference with neutral conditions. It also had the ability to grow in bile salts, which indicates its resistance to acid and bile salts. Also, the results of SDS-PAGE determined that the produced lacticin has a weight of about ۳.۱ KDa. Examination with Bradford's reagent showed that this bacterium produces lacticin with a concentration of ۴.۲ μg/μl. In addition, the scratch test results revealed that cancer cells treated with lacticin grew slower than the control sample. Also, the results of MTT indicated that more than ۸۰% of cancer cells were destroyed at a concentration of ۷ μg/ml, and its ۵۰% inhibitory concentration (IC۵۰) is ۵.۲ μg/ml.CONCLUSIONThe results of this study showed that the bacteriocin produced by Lactococcus lactis bacteria isolated from whey has the ability to inhibit the growth and also destroy MCF-۷ breast cancer cells, which shows the potential of this bacteriocin to fight and prevent breast cancer.