---

Abstract

Background and objectives:

important virulence factor for many invasive bacterial pathogens of humans.

Escherichia coli offer a model system to study the mechanisms by which

capsular polysaccharides are synthesized and exported onto the cell surface of

bacteria. Biosynthesis of the E

consists of the repeat structure -4) GlcA- (1, 4)-GlcNAc- (1-, requires the

KfiA, KfiB, KfiC, and KfiD proteins. Until now , the role of all proteins

except KfiB have been kown.

Capsular polysaccharide expression is an. coli K5 capsular polysaccharide, which

Material and Methods

(pMA1) and several derivatives of KfiB expression construct (pMA2-6) were

made with a 6Xhis-tag at the N-terminus. The presence of the hexa histidin tag

facilitated purification of the KfiB protein using Ni

: To study the role of the KfiB protein, a full-length2+-NTA chromatography.

Results:

pPC6::23 and restore capsule production. Successful complementation by

pMA1, showed that the fused hexa-histidine tag did not interrupt the function

of KfiB and that the full-length KfiB is required for complementation.

All plasmids except pMA1 failed to complement the mutation in

Roberts, I.S.

Conclusion:

cytoplasmic membrane.

Localization studies revealed that KfiB is associated with the

Key words:

Escherichia coli, Capsular polysaccharide, KfiB, K5

---

ABSTRACT
           Background and objective: Considering the toxic side effects of chemotherapy in treatment of cancer, anticancer drugs of natural origin including probiotic Lactobacillus strains have recently attracted a lot of attention.
Methods: After culturing chronic myeloid leukemia cell line K562 in 96-well plates, effects of different concentrations of culture supernatant from Lactobacillus casei on differentiation of the cells were investigated after 48 and 72 hours under an inverted microscope. Number of live cells and percentage of viable cells were determined by trypan blue exclusion test of cell viability. Cytotoxicity was assessed by MTT assay. Data analysis was performed by SPSS (version) 22 using one-way analysis of variance and Tukey's test at significance level of 0.05.
          Results: Secondary metabolites from the probiotic bacteria L. casei induced cellular differentiation, exerted anti-cancer effects and inhibited growth in K562 cells. Apoptotic cell death was confirmed by MTT and DNA fragmentation assays in a way that increasing the dilution from 1.2 to 1.32 significantly increased the viability of cells (P=0.001). In addition, increasing the dilution significantly increased the number of live cells in the first 48 hours (P=0.001).
        Conclusion: Culture supernatant of L. casei reduces the number of live cells, and induces apoptosis and monocytic differentiation in K562 cells in a dose- and time-dependent manner. Therefore, combined chemotherapy and differentiation therapy using such supernatants could be useful for treatment of cancer.
        Keywords: Cell differentiation, K562 cell line, Probiotic, Lactobacillus casei.

---