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  • 1
    In: Microbiology Spectrum, American Society for Microbiology, Vol. 10, No. 6 ( 2022-12-21)
    Abstract: Toxin-antitoxin (TA) systems are ubiquitous genetic elements in prokaryotes, but their biological importance is poorly understood. Mycobacterium smegmatis contains eight putative TA systems. Previously, seven TAs have been studied, with five of them being verified as functional. Here, we show that Ms0251-0252 is a novel TA system in that expression of the toxin Ms0251 leads to growth inhibition that can be rescued by the antitoxin Ms0252. To investigate the functional roles of TA systems in M. smegmatis , we deleted the eight putative TA loci and assayed the mutants for resistance to various stresses. Deletion of all eight TA loci resulted in decreased survival under starvation conditions and altered fitness when exposed to environmental stresses. Furthermore, we showed that deletion of the eight TA loci decreased resistance to phage infection in Sauton medium compared with the results using 7H10 medium, suggesting that TA systems might have different contributions depending on the nutrient environment. Furthermore, we found that MazEF specifically played a dominant role in resistance to phage infection. Finally, transcriptome analysis revealed that MazEF overexpression led to differential expression of multiple genes, including those related to iron acquisition. Altogether, we demonstrate that TA systems coordinately function to allow M. smegmatis to adapt to changing environmental conditions. IMPORTANCE Toxin-antitoxin (TA) systems are mechanisms for rapid adaptation of bacteria to environmental changes. Mycobacterium smegmatis , a model bacterium for studying Mycobacterium tuberculosis , encodes eight putative TA systems. Here, we constructed an M. smegmatis mutant with deletions of all eight TA-encoding genes and evaluated the resistance of these mutants to environmental stresses. Our results showed that different TA systems have overlapping and, in some cases, opposing functions in adaptation to various stresses. We suggest that complementary TA modules may function together to regulate the bacterial stress response, enabling adaptation to changing environments. Together, this study provides key insights into the roles of TA systems in resistance to various environmental stresses, drug tolerance, and defense against phage infection.
    Type of Medium: Online Resource
    ISSN: 2165-0497
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2022
    detail.hit.zdb_id: 2807133-5
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  • 2
    In: International Journal of Rheumatic Diseases, Wiley, Vol. 19, No. 7 ( 2016-07), p. 651-657
    Abstract: The aim of this study was to determine the efficacy and safety of a weekly dose of leflunomide (50 mg/week) in early rheumatoid arthritis patients with mild or moderate disease activity. Methods The patients of early rheumatoid arthritis (ERA) with mild or moderate disease activity were randomly selected for inclusion in this study and were assigned to either the treatment group (leflunomide 50 mg/week, LEF50) or the control group (leflunomide 10 mg/day, LEF10). All patients were treated for 24 weeks. Clinical efficacy was assessed using the disease activity score in 28 joints ( DAS 28) ‐ erythrocyte sedimentation rate (ESR) and European League Against Rheumatism ( EULAR ) response. A Chi‐squared test, Fisher's exact‐test and paired t ‐tests were used to analyze the data. Results A total of 244 patients who met the inclusion criteria and received at least one medicine dose were analyzed. At the baseline, the DAS 28 (ESR) of the ERA patients were 4.41 ± 0.69 in LEF 50 group and 4.52 ± 0.64 in LEF 10 group, respectively. At week 24, the DAS 28 (ESR) in two groups ( 2.94 ± 1.10 and 3.02 ± 1.14 ) were significant decreased compare with the baseline, respectively ( P 〈 0.01). There was no significant difference in DAS 28 (ESR) between the LEF50 and LEF10 groups at week 24. ( P  〉   0.05). At weeks 8, 12 and 24, the EULAR response (good responses + moderate responses) were 47.6%, 58.7% and 59.5%, in the LEF50 group and 43.2%, 49.1% and 53.4% in the LEF10 group, respectively. There was no significant different of EULAR response rates in the two groups at week 8, 12, and 24, respectively ( P 〉 0.05). There was no serious adverse events during the study. Conclusion A weekly dose of 50 mg leflunomide showed similar benefits to a daily dose of 10 mg leflunomide for the treatment of mild‐to‐moderate early rheumatoid arthritis.
    Type of Medium: Online Resource
    ISSN: 1756-1841 , 1756-185X
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2016
    detail.hit.zdb_id: 2427877-4
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  • 3
    Online Resource
    Online Resource
    American Society for Microbiology ; 2017
    In:  Applied and Environmental Microbiology Vol. 83, No. 17 ( 2017-09)
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 83, No. 17 ( 2017-09)
    Abstract: Clustered regularly interspaced short palindromic repeat (CRISPR)-Cas12a (Cpf1) has emerged as an effective genome editing tool in many organisms. Here, we developed and optimized a CRISPR-Cas12a-assisted recombineering system to facilitate genetic manipulation in bacteria. Using this system, point mutations, deletions, insertions, and gene replacements can be easily generated on the chromosome or native plasmids in Escherichia coli , Yersinia pestis , and Mycobacterium smegmatis . Because CRISPR-Cas12a-assisted recombineering does not require introduction of an antibiotic resistance gene into the chromosome to select for recombinants, it is an efficient approach for generating markerless and scarless mutations in bacteria. IMPORTANCE The CRISPR-Cas9 system has been widely used to facilitate genome editing in many bacteria. CRISPR-Cas12a (Cpf1), a new type of CRISPR-Cas system, allows efficient genome editing in bacteria when combined with recombineering. Cas12a and Cas9 recognize different target sites, which allows for more precise selection of the cleavage target and introduction of the desired mutation. In addition, CRISPR-Cas12a-assisted recombineering can be used for genetic manipulation of plasmids and plasmid curing. Finally, Cas12a-assisted recombineering in the generation of point mutations, deletions, insertions, and replacements in bacteria has been systematically analyzed. Taken together, our findings will guide efficient Cas12a-mediated genome editing in bacteria.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    RVK:
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2017
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 4
    In: The Scientific World Journal, Hindawi Limited, Vol. 2014 ( 2014), p. 1-7
    Abstract: A series of experiments have been carried out to investigate the effects of different concentrations of thapsigargin (0, 0.001, 0.1, and 1  μ M) on the proliferation and survival of human rheumatoid arthritis synovial cells (MH7A). The results showed that thapsigargin can block the cell proliferation in human rheumatoid arthritis synovial cells in a time- and dose-dependent manner. Results of Hoechst staining suggested that thapsigargin may induce cell apoptosis in MH7A cells in a time- and dose-dependent manner, and the percentages of cell death reached 44.6% at thapsigargin concentration of 1  μ M treated for 4 days compared to the control. The protein and mRNA levels of cyclin D1 decreased gradually with the increasing of thapsigargin concentration and treatment times. Moreover, the protein levels of mTORC1 downstream indicators pS6K and p4EBP-1 were reduced by thapsigargin treatment at different concentrations and times, which should be responsible for the reduced cyclin D1 expressions. Our results revealed that thapsigargin may effectively impair the cell proliferation and survival of MH7A cells. The present findings will help to understand the molecular mechanism of fibroblast-like synoviocytes proliferations and suggest that thapsigargin is of potential for the clinical treatment of rheumatoid arthritis.
    Type of Medium: Online Resource
    ISSN: 2356-6140 , 1537-744X
    Language: English
    Publisher: Hindawi Limited
    Publication Date: 2014
    detail.hit.zdb_id: 2075968-X
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  • 5
    Online Resource
    Online Resource
    Frontiers Media SA ; 2021
    In:  Frontiers in Genome Editing Vol. 3 ( 2021-12-8)
    In: Frontiers in Genome Editing, Frontiers Media SA, Vol. 3 ( 2021-12-8)
    Abstract: Multidrug-resistant Mycobacterium tuberculosis ( Mtb ) infection seriously endangers global human health, creating an urgent need for new treatment strategies. Efficient genome editing tools can facilitate identification of key genes and pathways involved in bacterial physiology, pathogenesis, and drug resistance mechanisms, and thus contribute to the development of novel treatments for drug-resistant tuberculosis . Here, we report a two-plasmid system, MtbCBE , used to inactivate genes and introduce point mutations in Mtb . In this system, the assistant plasmid pRecX-NucS E107A expresses RecX and NucS E107A to repress RecA-dependent and NucS-dependent DNA repair systems, and the base editor plasmid pCBE expresses a fusion protein combining cytidine deaminase APOBEC1, Cas9 nickase (nCas9), and uracil DNA glycosylase inhibitor (UGI). Together, the two plasmids enabled efficient G:C to A:T base pair conversion at desired sites in the Mtb genome. The successful development of a base editing system will facilitate elucidation of the molecular mechanisms underlying Mtb pathogenesis and drug resistance and provide critical inspiration for the development of base editing tools in other microbes.
    Type of Medium: Online Resource
    ISSN: 2673-3439
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 3017800-9
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  • 6
    Online Resource
    Online Resource
    Elsevier BV ; 2009
    In:  Journal of Reproduction and Contraception Vol. 20, No. 4 ( 2009-12), p. 217-221
    In: Journal of Reproduction and Contraception, Elsevier BV, Vol. 20, No. 4 ( 2009-12), p. 217-221
    Type of Medium: Online Resource
    ISSN: 1001-7844
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2009
    detail.hit.zdb_id: 2389672-3
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  • 7
    In: Asian Journal of Andrology, Medknow, Vol. 7, No. 1 ( 2005-3), p. 70-70
    Type of Medium: Online Resource
    ISSN: 1008-682X , 1745-7262
    Language: Unknown
    Publisher: Medknow
    Publication Date: 2005
    detail.hit.zdb_id: 2085228-9
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  • 8
    In: Science Advances, American Association for the Advancement of Science (AAAS), Vol. 8, No. 47 ( 2022-11-25)
    Abstract: Development of combined CRISPRi and CRISPR-KO screening provides a comprehensive functional genomics study platform in Mtb.
    Type of Medium: Online Resource
    ISSN: 2375-2548
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2022
    detail.hit.zdb_id: 2810933-8
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  • 9
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2016
    In:  Scientific Reports Vol. 6, No. 1 ( 2016-03-14)
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 6, No. 1 ( 2016-03-14)
    Abstract: Research on mycobacterial genetics relies heavily on techniques for directed gene mutation, but genetic studies are often hampered by the difficulty of generating gene deletions in mycobacteria. We developed an efficient and improved deletion system, described here in detail, which can be used to construct multiple unmarked recombinants in mycobacteria. We tested this system by using it to sequentially delete four pairs of toxin-antitoxin genes in Mycobacterium smegmatis .
    Type of Medium: Online Resource
    ISSN: 2045-2322
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2016
    detail.hit.zdb_id: 2615211-3
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  • 10
    Online Resource
    Online Resource
    Trans Tech Publications, Ltd. ; 2017
    In:  Key Engineering Materials Vol. 726 ( 2017-1), p. 55-59
    In: Key Engineering Materials, Trans Tech Publications, Ltd., Vol. 726 ( 2017-1), p. 55-59
    Abstract: As an important type of additive, the redispersible powder is widely applied in cement-based and gyp-based materials, so as to improve the cementing strength, impermeability, workability, hydrophobicity and so on. However, the chemical composition of the redispersible powders determines its applicability, as well as the degree of improvement to the matrix materials. In this paper, the chemical composition of an unknown redispersible powder was analyzed by several instruments. Firstly, Fourier transform infrared spectroscopy (FTIR) analysis indicated that the polymer was polymerized with monomers of vinyl esters. Secondly, pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) analysis showed the pyrolysis products were mainly acetic acid, methyl acetate and methyl versatates. Considering the pyrolysis mechanism of synthetic polymers and the results from FTIR spectra, the polymer in the redispersible powder was deduced to be the copolymer of vinyl acetate and vinyl ester of versatic acid (VeoVa), which was a monomer with a unique highly branched carbon-rich structure. Thermogravimetry (TG) analysis revealed that the powder contained 74.0% of polymer, 14.5% of calcium carbonate and 11.4% of other inorganic materials.
    Type of Medium: Online Resource
    ISSN: 1662-9795
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2017
    detail.hit.zdb_id: 2073306-9
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