Selective Cytotoxic effect of Probiotic, Paraprobiotic and Postbiotics of L. casei strains against Colorectal Cancer Cells: Invitro studies

Abstract This study highlights the cytotoxic effect of three L. casei strains on colorectal cell lines in invitro conditions. Different concentrations of live, heat killed (HK) and cell free supernatant (CFS) of three L.casei strains were subjected to CaCo2 and MRC5 cell lines. The viability of the treated and untreated cells was determined after 72 hrs by MTT assay, and IC50 estimated. Apoptosis was evaluated by Annexin V-propidium iodide method using flow cytometry. The live, HK and CFS of the L. casei strains showed cytotoxic effects on colorectal cell lines with significant differences. The cytotoxicity effects of live cells on CaCo2 cells were significantly higher (p˂0.01) than the HK cells. A dose dependent response was observed, as higher concentrations resulted in enhanced cytotoxicity effects. Live L.casei 1296-2cells inhibited 91% of CaCo2 cell growth, with IC50 of less than 108 cfu/ml. MRS medium and concentrations of CFS at above 20% v/v, were cytotoxic to the normal cell lines. Flow cytometry analyses of L. casei 1296-2 indicated that cytotoxicity effects on CaCo2 cells is related to apoptotic induction. Invitro studies indicate that Live and CFS of L. casei 1296-2 might be promising candidate for the control of colorectal cancers

Plasmid associated lactocin RN78 production in a lactobacillus RN78 strain isolated from a dairy sample in Iran

A bacteriocin, lactocin RN78 produced by a Lactobacillus RN78 strain isolated previously from a cheese sample, was found inhibitory against many pathogenic Gram-negative and Gram-positive bacteria including Kl. pneumoniae, L. ivanovii, L. monocytogenes, Ps. aeruginosa, and S. aureus. Characterization of the inhibitory agent produced by RN78 strain revealed it to be heat stable [100 and 121°C for 90 and 15 minutes respectively], and active at wide pH range of 3 to 9. Moreover, the inhibitory activity was completely destroyed after treatment with proteolytic enzymes [Pronase and Trypsin]; while no change in its antimicrobial activity was recorded after treatment with the enzyme catalase. A rapid cell death of the indicator strain [106 to 107 cells] within 2 hours of incubation in presence of 10240 AU mL[-1] of lactocin RN78 indicated the bactericidal nature of this bacteriocin against L. monocytogenes. Treatment of lactocin RN78 with 0.5 mM EDTA resulted in expansion of the inhibitory spectrum and it inhibited the growth of E. coli and S. typhi to which it was previously non-influential. Curing of the producer strain RN78 with acridine orange resulted in Bac-mutant defective in bacteriocin production. Plasmid analysis of the wild type and mutant's defective in bacteriocin production indicated the absence of a 42Kb plasmid that was originally present in the wild producer strain. All the cured strains retained their immunity to lactocin RN78 which indicated the possibility of the immunity genes to be on the chromosomes instead of being on the plasmid RN