Heterologous Expression of Pediocin/Papa in Bacillus Subtilis

Listeria moniocytogenes is food-borne pathogen. Pediocin is group II α bacteriocin with anti-listeria activity, naturally produced by Pediococuus acidilactic and Lactobacillus plantarum. Gene pepA/papA encode for pediocin. Expression and secretion of active papA was relayed on transporter papC and accessary protein papD on the same operon in native host. The excretion machines were also necessary for pediocin protein expression in heterologous host of E. coli, Lactobacillus lactis, and Corynebacterium glutamicum. In this study, two vector carrying codon sequence of papA mature peptide was constructed, with or without His tag. Both fragments were inserted into plasmid pHT43 and transformed Bacillus subtilis WB800N. The strains were induced with IPTG to secrete recombination protein PA1 and PA2 respectively. Supernatant from both recombination strains can inhibit Listeria monocytogenes ATCC54003 directly. The fused protein possesses inhibition activity as a whole, exempting from cleavage of leading peptide. Protein PA1 can be purified by nickel-nitrilotriacetic acid (Ni-NTA) metal affinity chromatography. This is the first report for active pediocin expression without assistance of papCD in heterogenous host.

Siderophore-mediated zinc acquisition enhances enterobacterial colonization of the inflamed gut

Zinc is an essential cofactor for bacterial metabolism, and many Enterobacteriaceae express the zinc transporters ZnuABC and ZupT to acquire this metal in the host. However, the probiotic bacterium Escherichia coli Nissle 1917 (or “Nissle”) exhibits appreciable growth in zinc-limited media even when these transporters are deleted. Here, we show that Nissle utilizes the siderophore yersiniabactin as a zincophore, enabling Nissle to grow in zinc-limited media, to tolerate calprotectin-mediated zinc sequestration, and to thrive in the inflamed gut. We also show that yersiniabactin’s affinity for iron or zinc changes in a pH-dependent manner, with increased relative zinc binding as the pH increases. Thus, our results indicate that siderophore metal affinity can be influenced by the local environment and reveal a mechanism of zinc acquisition available to commensal and pathogenic Enterobacteriaceae.

Serological responses to a soluble recombinant circumsporozoite protein-VK210 of Plasmodium vivax (rPvCSP-VK210) among Iranian malaria patients

Background Circumsporozoite protein (CSP) has a central immune domain that includes short regions of repeating amino acid sequences. This immunodynamic region is an epitope of B cells that can elicit an immune response in human and laboratory animals. The aim of the present study was to express the recombinant PvCSP-VK210 antigen and evaluate it for assaying antibodies obtained during human P. vivax infection by Western blotting and indirect ELISA (enzyme-linked immunosorbent assay). Method Genomic DNA of P. vivax was isolated from a blood sample of an Iranian person with vivax malaria, and by PCR, the fragment of the PvCSP-VK210 gene was amplified. The gene fragment was cut after gel purification by BamHI and HindIII enzymes and then cloned into pET28a expression vector. Finally, the recombinant pET28a was transformed into the E.coli BL21 (DE3) as the expression host. In order to produce His-tagged protein, the expression host was cultured in LB medium. The protein was purified by Ni–NTA columns and immobilized metal affinity chromatography, and after confirmation by Western blotting technique, was used as the antigen in the indirect ELISA test. Results The recombinant protein was expressed and purified as a 32-kDa protein. The sensitivity and specificity of the indirect ELISA test with the recombinant PvCSP-VK210 antigen were 61.42% and 97.14%, respectively, based on OD = 0.313. Between the results of the microscopic test and the indirect ELISA test with the recombinant PvCSP-VK210 antigen there was a Kappa coefficient of 0.586. The positive and negative predictive value and validity of the ELISA test with the recombinant PvCSP-VK210 antigen were 95.55%, 71.57%, 79.28%, respectively. Conclusion The sensitivity of the indirect ELISA method with the recombinant PvCSP-VK210 antigen was 61.42%, which is the first report from Iran.

Purification and Identification of Novel Xanthine Oxidase Inhibitory Peptides Derived from Round Scad (Decapterus maruadsi) Protein Hydrolysates

The objective of the present study was to investigate the xanthine oxidase (XO) inhibitory effects of peptides purified and identified from round scad (Decapterus maruadsi) hydrolysates (RSHs). In this study, RSHs were obtained by using three proteases (neutrase, protamex and alcalase). Among them, the RSHs of 6-h hydrolysis by neutrase displayed the strongest XO inhibitory activity and had an abundance of small peptides (<500 Da). Four novel peptides were purified by immobilized metal affinity chromatography and identified by nano-high-performance liquid chromatography mass/mass spectrometry. Their amino acid sequences were KGFP (447.53 Da), FPSV (448.51 Da), FPFP (506.59 Da) and WPDGR (629.66 Da), respectively. Then the peptides were synthesized to evaluate their XO inhibitory activity. The results indicated that the peptides of both FPSV (5 mM) and FPFP (5 mM) exhibited higher XO inhibitory activity (22.61 ± 1.81% and 20.09 ± 2.41% respectively). Fluorescence spectra assay demonstrated that the fluorescence quenching mechanism of XO by these inhibitors (FPSV and FPFP) was a static quenching procedure. The study of inhibition kinetics suggested that the inhibition of both FPSV and FPFP was reversible, and the type of their inhibition was a mixed one. Molecular docking revealed the importance of π-π stacking between Phe residue (contained in peptides) and Phe914 (contained in the XO) in the XO inhibitory activity of the peptides.

EXPRESSION OF THE STAPHYLOCOCCUS AUREUS LUKE GENE IN THE ESCHERICHIA COLI BL21(DE3) STRAIN

Two-component leukotoxins are important virulence factors for Staphylococcus aureus. Despite efforts made to study S. aureus leukotoxins, the direct mechanism of action of these toxins during infection has not been determined. However, the observation that deletion of LukED significantly attenuates highly virulent S. aureus strains supports the hypothesis that selective inhibition of LukE / D may be useful in the development of new aspects of S. aureus infection control. For this purpose, this work was carried out to test the expression and obtain a recombinant form of the LukE protein in E.coli cells. The LukE gene was cloned into the pET28-c (+) / GFP vector containing the gfp gene. Two fused genes carrying a hexahistidine tag were expressed in cells of the E. coli BL21(DE3) strain. It was found that the 6His-GFP-LucE protein aggregates in inclusion bodies. 6His-GFP-LucE was washed out of inclusion bodies with high molar urea. The 6His-GFP-LucE protein was purified by metal affinity chromatography. Research results can be applied to obtain recombinant protein including strategies for inhibition of toxin activity.

Development of Human Toxo IgG ELISA Kit, and False-Positivity of Latex Agglutination Test for the Diagnosis of Toxoplasmosis

Toxoplasma gondii is an intracellular zoonotic parasite that causes infection in a wide range of warm-blooded animals and humans. The main aim of this studywas to assess the diagnostic value of the recombinant SAG1 antigen (rSAG1) for T. gondii-IgG screening through the Human Toxo IgG ELISA Kit (K). The rSAG1 was expressed in E. coli (DE3), and it was purified through metal-affinity chromatography. The rSAG1 was confirmed by immunoblotting, and it had a band on 35 kDa.Total of 400 human sera were tested by LAT and K. One hundred and twenty-two (30.5%) sera were found positive by LAT and eighty-nine (22.25%) sera were found positive by K.Out of 400 samples, 80 were selected to evaluate the performance of K through commercial Toxoplasma gondii IgG ELISA Kit (C). Out of 80 human sera, 55 (68.75%) were found positive, 25 (31.25%) were found negative by K and C, respectively. The cut-off value for K was 0.398 and it was calculated through the receiver operator characteristic curve. The ELISA plates were coated at optimized concentration of rSAG1 = 0.125 µg/mL, and the test was performed by diluting the sera at 1:50. The sensitivity and specificity of K were observed to be 98.5% and 100%, respectively. The six sera (K-L+were found positive through LAT and these human sera were later evaluated by Western blot analysis. These sera did not produce a band equivalent to 35 kDa on WB analysis thus, LAT produced false-positive results

OPTIMIZACIÓN DE LA EXTRACCIÓN Y PURIFICACIÓN DE UNA β-CAROTENO 15,15’-MONOOXIGENASA RECOMBINANTE A PARTIR DE CUERPOS DE INCLUSIÓN

Los forrajes utilizados en la producción de ganado bovino en el trópico tienen altos niveles de β-caroteno, que produce canales con grasa de color amarillo y demerita su valor económico. La pigmentación amarilla se debe a la actividad baja de la enzima β -caroteno 15,15’-monooxigenasa (BCMO1) en el intestino delgado e hígado. Un uso biotecnológico de esta enzima podría escindir al β -caroteno en dos moléculas de retinal, eliminar la fuente de coloración y optimizar el valor comercial de la carne del ganado bovino alimentado en pastoreo. El objetivo de este estudio fue obtener una enzima BCMO1 recombinante con actividad similar a las enzimas nativas, a partir de bacterias transformadas con el gen que codifica la b-caroteno 15,15’-monooxigenasa de Gallus gallus (gBCMO1). La enzima se obtuvo por sobre expresión a partir de una Escherichia coli XL1-Blue transformada con dicho gen, y se purificó por Cromatografía rápida de proteína líquida (Fast Protein Liquid Chromatography, FPLC); se midió la actividad in vitro del proceso por Cromatografía de afinidad por metales inmovilizados (Immobilized Metal Affinity Chromatography, IMAC) y el producto final se detectó por Cromatografía de líquidos de polaridad alta (High Polarity Liquid Chromatography, HPLC). Una proteína de aproximadamente 63 kDa se obtuvo, la cual presentó una actividad enzimática de 2993 (± 108.2) pmol mg-1 de proteína h-1 (n=3). La proteína aislada se puede evaluar como aditivo en estudios in vitro con el fin de disminuir la coloración amarilla de las canales de bovinos.