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  • 1
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    OmpF of Pectobacterium carotovorum subsp. carotovorum Pcc3 is required for carocin D sensitivity (2016)
    Oxford University Press
    Details
    Publication Date: 2016-12-23
    Description: Carocin D is a bacteriocin produced by Pectobacterium carotovorum subsp. carotovorum Pcc21. Carocin D inhibits the growth of P . carotovorum subsp. carotovorum and closely related strains. Pectobacterium carotovorum subsp. carotovorum is a causative bacterium for soft rot disease and leads to severe economic losses. Bacteriocins recognize and interact with a specific membrane protein of target bacteria as a receptor. To identify the receptor responsible for carocin D recognition, mutants that underwent a phenotypic change from carocin D sensitivity to carocin D insensitivity were screened. Based on Tn 5 insertions, carocin D sensitivity was dependent on expression of the outer membrane protein OmpF. The insensitivity of the mutant (Pcc3MR) to carocin D was complemented with ompF from carocin D-sensitive strains, not from carocin D-resistant strains. The selectivity between sensitive and resistant strains could be attributed to variation in OmpFs in the cell-surface-exposed regions. Based on sequence analysis and complementation assays, it appears that carocin D uses OmpF as a receptor and is translocated by the TonB system. According to previously reported translocation mechanisms of colicins, OmpF works along with the TolA system rather than the TonB system. Therefore, the current findings suggest that carocin D is imported by a unique colicin-like bacteriocin translocation system.
    Keywords: Biotechnology & Synthetic Biology
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 2
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    The enhanced immune responses induced by Salmonella enteritidis ghosts loaded with Neisseria gonorrhoeae porB against Salmonella in mice (2016)
    Oxford University Press
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    Publication Date: 2016-12-16
    Description: Human health has been seriously endangered by highly prevalent salmonellosis and multidrug-resistant Salmonella strains. Current vaccines suffer from variable immune-protective effects, so more effective ones are needed to control Salmonella infection . Bacterial ghosts have been produced by the expression of lysis gene E from bacteriophage PhiX174 and can be filled with considerable exogenous substances such as DNA or drugs as a novel platform. In this study, Salmonella enteritidis (SE) ghosts were developed and loaded with Neisseria gonorrhoeae porin B (porB) to construct a novel inactive vaccine. Our new studies show that SE ghosts loaded with porB displayed increased production of pro-inflammatory cytokines (IL-1β, IL-6, IL-10 and IL-12p70) in bone marrow-derived dendritic cells (BMDCs), and elicited significantly higher specific systemic and mucosal immune responses to Salmonella than SE ghosts alone. In addition, the novel porB-loaded ghosts conferred higher protective effects on virulent Salmonella challenge. For the first time, we demonstrate that N. gonorrhoeae porB, as a novel adjuvant, can increase the immunogenicity of SE ghosts. Our studies suggested that Salmonella enteritidis ghosts loaded with Neisseria gonorrhoeae porin B might be a useful mucosal Salmonella vaccine candidate for practical use in the future.
    Keywords: Biotechnology & Synthetic Biology
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 3
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    Expression of biologically active murine interleukin-18 in Lactococcus lactis (2016)
    Oxford University Press
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    Publication Date: 2016-12-12
    Description: The food-grade bacterium Lactococcus lactis is increasingly used for heterologous protein expression in therapeutic and industrial applications. The ability of L. lactis to secrete biologically active cytokines may be used for the generation of therapeutic cytokines. Interleukin (IL)-18 enhances the immune response, especially on mucosal surfaces, emphasizing its therapeutic potential. However, it is produced as an inactive precursor and has to be enzymatically cleaved for maturation. We genetically manipulated L. lactis to secrete murine IL-18. The mature murine IL-18 gene was inserted downstream of a nisin promoter in pNZ8149 plasmid and the construct was used to transform L. lactis NZ3900 . The transformants were selected on Elliker agar and confirmed by restriction enzyme digestion and sequencing. The expression and secretion of IL-18 protein was verified by SDS-PAGE, western blotting and ELISA. The biological activity of recombinant IL-18 was determined by its ability to induce interferon (IFN)- production in L. lactis co-cultured with murine splenic T cells. The amounts of IL-18 in bacterial lysates and supernatants were 3–4 μg mL –1 and 0.6–0.7 ng mL –1 , respectively. The successfully generated L. lactis strain that expressed biologically active murine IL-18 can be used to evaluate the possible therapeutic effects of IL-18 on mucosal surfaces.
    Keywords: Biotechnology & Synthetic Biology
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 4
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    RAG1 targeting in the genome is dominated by chromatin interactions mediated by the non-core regions of RAG1 and RAG2 (2016)
    Oxford University Press
    Details
    Publication Date: 2016-12-01
    Description: The RAG1/RAG2 endonuclease initiates V(D)J recombination at antigen receptor loci but also binds to thousands of places outside of these loci. RAG2 localizes directly to lysine 4 trimethylated histone 3 (H3K4me3) through a plant homeodomain (PHD) finger. The relative contribution of RAG2-dependent and RAG1-intrinsic mechanisms in determining RAG1 binding patterns is not known. Through analysis of deep RAG1 ChIP-seq data, we provide a quantitative description of the forces underlying genome-wide targeting of RAG1. Surprisingly, sequence-specific DNA binding contributes minimally to RAG1 targeting outside of antigen receptor loci. Instead, RAG1 binding is driven by two distinct modes of interaction with chromatin: the first is driven by H3K4me3, promoter-focused and dependent on the RAG2 PHD, and the second is defined by H3K27Ac, enhancer-focused and dependent on ‘non-core’ portions of RAG1. Based on this and additional chromatin and genomic features, we formulated a predictive model of RAG1 targeting to the genome. RAG1 binding sites predicted by our model correlate well with observed patterns of RAG1-mediated breaks in human pro-B acute lymphoblastic leukemia. Overall, this study provides an integrative model for RAG1 genome-wide binding and off-target activity and reveals a novel role for the RAG1 non-core region in RAG1 targeting.
    Keywords: Genomics
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 5
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    Enterotoxigenic Escherichia coli heat-stable toxin and heat-labile toxin toxoid fusion 3xSTaN12S-dmLT induces neutralizing anti-STa antibodies in subcutaneously immunized mice (2016)
    Oxford University Press
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    Publication Date: 2016-11-17
    Description: Enterotoxigenic Escherichia coli (ETEC) bacteria producing heat-stable toxin (STa) and/or heat-labile toxin (LT) are among top causes of children's diarrhea and travelers’ diarrhea. Currently no vaccines are available for ETEC associated diarrhea. A major challenge in developing ETEC vaccines is the inability to stimulate protective antibodies against the key STa toxin that is potently toxic and also poorly immunogenic. A recent study suggested toxoid fusion 3xSTa N12S -dmLT, which consists of a monomer LT toxoid (LT R192G/L211A ) and three copies of STa toxoid STa N12S , may represent an optimal immunogen inducing neutralizing antibodies against STa toxin [IAI 2014, 82(5):1823-32]. In this study, we immunized mice with this fusion protein following a different parenteral route and using different adjuvants to further characterize immunogenicity of this toxoid fusion. Data from this study showed that 3xSTa N12S -dmLT toxoid fusion induced neutralizing anti-STa antibodies in the mice following subcutaneous immunization, as effectively as in the mice under intraperitoneal route. Data also indicated that double mutant LT (dmLT) can be an effective adjuvant for this toxoid fusion in mice subcutaneous immunization. Results from this study affirmed that toxoid fusion 3xSTa N12S -dmLT induces neutralizing antibodies against STa toxin, suggesting this toxoid fusion is potentially a promising immunogen for ETEC vaccine development.
    Keywords: Biotechnology & Synthetic Biology
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 6
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    Recombineering and I-SceI-mediated Pseudomonas putida KT2440 scarless gene deletion (2016)
    Oxford University Press
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    Publication Date: 2016-11-17
    Description: Pseudomonas putida KT2440 is a saprophytic and generally recognized as safe microorganism that plays important roles in the biodegradation and production of value-added chemicals. Chromosomal gene deletion of P. putida KT2440 usually involves time-consuming gene cloning, conjugal transfer and counterselection. Recently, we developed a P. putida KT2440 markerless gene deletion method based on recombineering and Cre/ loxP site-specific recombination. PCR-based Red recombineering circumvents the tedious cloning steps and is more amenable to high-throughput manipulation. Here we report an improved scarless gene deletion strategy based on recombineering and intron-encoded homing endonuclease I-SceI-mediated double-strand break repair. Sixteen drug exporter gene(s) were deleted and the minimal inhibition concentrations of the mutants to a variety of antibiotics were determined. The robustness of the procedure was also demonstrated by sequential deletion of five large genomic regions. Up to 59% recombination efficiency was achieved for a 54.8 kb deletion, and the efficiency of RecA-mediated double-strand break repair, which was boosted by Red recombinase, was nearly 100%. The strain with a 3.76% genome reduction showed an improved growth rate and transformation efficiency. The straightforward, time-saving and highly efficient scarless deletion approach has the potential to facilitate the genetic study, and biotechnological and environmental applications of P. putida KT2440.
    Keywords: Biotechnology & Synthetic Biology
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 7
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    Preparation and evaluation of MS2 bacteriophage-like particles packaging hepatitis E virus RNA (2016)
    Oxford University Press
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    Publication Date: 2016-11-09
    Description: Hepatitis E virus (HEV) is the pathogen causing hepatitis E (HE). It arouses global public health concern since it is a zoonotic disease. The objective of this letter is to report a cost-effective internal control prepared for monitoring procedures of HEV reverse transcriptase (RT)-PCR detection. A selected conserved HEV RNA fragment was integrated into the downstream of the truncated MS2 bacteriophage genome based on Armored RNA technology. The resulting MS2-HEV gene harbored by the pET-28b-MS2-HEV plasmid was transformed into E. coli BL21(DE3) for expression analysis by SDS-PAGE. The expression products were purified and concentrated by ultrasonication and ultrafiltration separation. The morphology and stability properties of the virus-like particles (VLPs) were evaluated by electron microscopy scanning and nuclease challenges, respectively. SDS-PAGE results showed that the constructed MS2-HEV gene expressed efficiently and the purity of the VLPs was highly consistent with the result in electron microscopy. Stability evaluation results demonstrated that the prepared VLPs exhibited strong resistance to DNase I and RNase A attacks and also performed long-lasting protection of coated HEV RNA for at least 4 months at –20°C. These data revealed that the prepared VLPs meet the basic requirements of use as internal control material in the HEV RNA amplification assay.
    Keywords: Biotechnology & Synthetic Biology
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 8
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    Elimination of unaltered DNA in mixed clinical samples via nuclease-assisted minor-allele enrichment (2016)
    Oxford University Press
    Details
    Publication Date: 2016-11-01
    Description: Presence of excess unaltered, wild-type (WT) DNA providing no information of biological or clinical value often masks rare alterations containing diagnostic or therapeutic clues in cancer, prenatal diagnosis, infectious diseases or organ transplantation. With the surge of high-throughput technologies there is a growing demand for removing unaltered DNA over large pools-of-sequences. Here we present nuclease-assisted minor-allele enrichment with probe-overlap (NaME-PrO), a single-step approach with broad genome coverage that can remove WT-DNA from numerous sequences simultaneously, prior to genomic analysis. NaME-PrO employs a double-strand-DNA-specific nuclease and overlapping oligonucleotide-probes interrogating WT-DNA targets and guiding nuclease digestion to these sites. Mutation-containing DNA creates probe-DNA mismatches that inhibit digestion, thus subsequent DNA-amplification magnifies DNA-alterations at all selected targets. We demonstrate several-hundred-fold mutation enrichment in diverse human samples on multiple clinically relevant targets including tumor samples and circulating DNA in 50-plex reactions. Enrichment enables routine mutation detection at 0.01% abundance while by adjusting conditions it is possible to sequence mutations down to 0.00003% abundance, or to scan tumor-suppressor genes for rare mutations. NaME-PrO introduces a simple and highly parallel process to remove un-informative DNA sequences and unmask clinically and biologically useful alterations.
    Keywords: Genomics
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 9
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    The endolysin from the Enterococcus faecalis bacteriophage VD13 and conditions stimulating its lytic activity (2016)
    Oxford University Press
    Details
    Publication Date: 2016-10-12
    Description: Bacteriophages produce endolysins (peptidoglycan hydrolases) to lyse the host cell from within and release nascent bacteriophage particles. Recombinant endolysins can lyse Gram-positive bacteria when added exogenously. As a potential alternative antimicrobial, we cloned and expressed the enterococcal VD13 bacteriophage endolysin. VD13 endolysin has a CHAP catalytic domain with 92% identity with the bacteriophage IME-EF1 endolysin. The predicted size of VD13 endolysin is ~27 kDa as verified by SDS-PAGE. The VD13 endolysin lyses Enterococcus faecalis strains, but not E. faecium or other non-enterococci. VD13 endolysin has activity from pH 4 to pH 8, with peak activity at pH 5, and exhibits greater activity in the presence of calcium. Optimum activity at pH 5 occurs in the absence of NaCl. VD13 endolysin, in ammonium acetate (C 2 H 3 O 2 NH 4 ) calcium chloride (CaCl 2 ) buffer pH 5, is stimulated to higher activity upon heating at temperatures up to 65°C for 30 min, whereas activity is lost upon heating to 42°C, in pH 7 buffer.
    Keywords: Biotechnology & Synthetic Biology
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 10
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    A simple technique for suppressor detection in Escherichia coli (2016)
    Oxford University Press
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    Publication Date: 2016-10-12
    Description: To study the viability of a gyrA S83 stop mutation found in an Escherichia coli J53 ciprofloxacin-resistant strain (J53 CipR27), a pBR322 derivative was constructed with a TAG mutation in the bla gene knocking out ampicillin resistance. Ampicillin resistance was restored, suggesting that the strain contains tRNA suppressor activity able to suppress the UAG codon gyrA and allow viability. The method was applied to 22 unique clinical E. coli isolates, and all were found to have low-level suppressor activity.
    Keywords: Biotechnology & Synthetic Biology
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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