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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The aetiological agent of tuberculosis, Mycobacterium tuberculosis, encodes 13 σ factors, as well as several putative anti-, and anti-anti- σ factors. Here we show that a σ factor that has been previously shown to be involved in virulence and persistence processes, σF, can be specifically inhibited by the anti-σ factor UsfX. Importantly, the inhibitory activity of UsfX, in turn, can be negatively regulated by two novel anti-anti-σ factors. The first anti-anti-σ factor seems to be regulated by redox potential, and the second may be regulated by phosphorylation as it is rendered non-functional by the introduction of a mutation that is believed to mimic phosphorylation of the anti-anti-σ factor. These results suggest that σF activity might be post-translationally modulated by at least two distinct pathways in response to different possible physiological cues, the outcome being consistent with the bacteria's ability to adapt to diverse host environments during disease progression, latency and reactivation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 81 (1991), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: A cloning cassette, carrying a modified aminoglycoside resistance gene (neo) from transposon Tn5 was constructed. Three restriction sites internal to the neo gene were eliminated by in vitro mutagenesis, allowing their use in designing new cloning vectors. The original, suboptimal transcription promoter was replaced with a synthetic sequence corresponding to the consensus for E. coli and Streptomyces promoters. The cassette has numerous restriction sites for easy subcloning of the promoter, the coding sequence or the whole gene.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 38 (1992), S. 188-193 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A highly efficient chitosanase producer, the actinomycete N174, identified by chemotaxonomic methods as belonging to the genus Streptomyces was isolated from soil. Chitosanase production by N174 was inducible by chitosan or d-glucosamine. In culture filtrates the chitosanase accounted for 50–60% of total extracellular proteins. The chitosanase was purified by polyacrylic acid precipitation, CM-Sepharose and gel permeation chromatography. The maximum velocity of chitosan degradation was obtained at 65° C when the pH was maintained at 5.5. The enzyme degraded chitosans with a range of acetylation degrees from 1 to 60% but not chitin or CM-cellulose. The enzyme showed an endo-splitting type of activity and the end-product of chitosan degradation contained a mixture of dimers and trimers of d-glucosamine.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature structural biology 3 (1996), S. 155-162 
    ISSN: 1072-8368
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] We report the 2.4 Å X-ray crystal structure of a protein with chitosan endo-hydrolase activity isolated from Streptomyces N174. The structure was solved using phases acquired by SIRAS from a two-site methyl mercury derivative combined with solvent flattening and non-crystallographic two-fold ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell reports 15 (1995), S. 222-226 
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Growth inhibition towards Rhizopus nigricans, Fusarium oxysporum f. sp. radicis-lycopersici, Verticillium albo-atrum and Pythium ultimum was observed in vitro using a purified chitosanase from an actinomycete, Streptomyces sp, strain N174. The corresponding gene, with its own signal peptide, was inserted into pBI121.7 shuttle vector to transform tobacco. Transgenic plants were analysed for chitosanase activity by a sodium dodecyl sulfate-polyacrylamide gel electrophoresis assay. Two major and one minor active electrophoretic forms were detected in transgenic tobacco. Some chitosanases were recovered not only in leaf homogenates but also in leaf intercellular fluid extracts. One chitosanase electrophoretic form migrated very closely to the purified Streptomyces mature protein while the others corresponded to molecules of higher molecular mass. The N-terminus sequence was determined for one of the three chitosanase forms. It exhibited a different signal peptide cleavage site when compared to the mature chitosanase from Streptomyces. This is the first report on the expression of an active chitosanase gene with antimicrobial potential in plants.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 156 (1991), S. 192-197 
    ISSN: 1432-072X
    Keywords: Streptomyces lividans ; Chitin ; Chitosan ; Chitinase ; N-Acetylglucosaminidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Streptomyces lividans TK24, an established host for genetic and molecular studies in actinomycetes, is able to use chitin as sole carbon and nitrogen source. Extracellular chitinase and N-acetyl-β-d-glucosamidinase (chitobiase) activities were detected in liquid cultures. Chitinase production was inducible by chitin and its low molecular weight derivatives. Low levels of chitinase were also produced in the absence of chitin. Production of extracellular N-acetylglucosaminidase was correlated with the beginning of the stationary phase of growth and was independent of the presence of chitin. Beside highly N-acetylated chitin, supernatants of chitin-induced cultures were able to hydrolyse chitosans with a wide range of degrees of N-acetylation.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-4927
    Keywords: alcohol dehydrogenase ; soybean ; flooding ; isozymes ; DNA homology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Molecular properties of alcohol dehydrogenase (ADH) were examined in young soybean seedlings. Soybean radicle tissue is ADH-rich. Enzyme specific activity decreases slowly with the development of roots and becomes almost undetectable when the first true leaves appear. Soybean ADH was not found to be inducible by flooding. 2,4-Dichlorophenoxyacetic acid (2,4-D) treatment increased ADH specific activity as much as 14-fold. Only one ADH isozyme was detected by isoelectric focusing. By DNA-DNA hybridization, soybean ADH genomic sequences were shown to be partly homologous to maize ADH1 cDNA. The presence of more than one Adh gene in soybean is discussed.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The chitosanase gene from a new soil isolate, the actinomyceteKitasatosporia N174, was cloned inStreptomyces lividans TK24. The enzyme expressed from the cloned gene had a molecular weight of approximately 29,500; an isoelectric point of 7.5 and was indistinguishable from the purified N174 chitosanase.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 118 (2000), S. 377-393 
    ISSN: 1573-2932
    Keywords: air ; biofiltration ; treatment ; xylenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Biofiltration of air polluted by VOCs is now beingrecognized by the industrial and research communitiesto be an effective and viable alternative for theclassical environmental technologies. While a numberof biological aspects of the biofiltration process arewell understood, the effect of certain engineeringparameters such as temperature, pressure drop,bacterial count, etc., remained ambiguous especiallywhen several isomers have to be removedsimultaneously. In this paper are reported theresults of purification of air containing vapors ofxylenes in a laboratory-scale biofilter reactor. Thelatter is a packed bed of peat balls particlesspecifically designed and produced for this purpose. Three types of micro-organisms strains werescrutinizingly selected and immobilized on thefiltering material. Xylenes entering the biofilter ata relatively high inlet load (110 g m-3 h-1)are removed with an elimination capacity of60 g m-3 h-1 (at steady state). Theexperimental results obtained on the reduction ofxylenes were satisfactorily represented by thegeneralized Ottengraf's model.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Chemical Technology AND Biotechnology 73 (1998), S. 183-196 
    ISSN: 0268-2575
    Keywords: biofiltration ; peat ; biodegradation ; toluene ; xylene ; inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Air biofiltration is now under active consideration for the removal of the volatile organic compounds from air polluted streams. In order to investigate the performance of this newly developed technology, a biofiltration pilot unit was operated for a continuous period of 8 months. The biofilter column was packed with commercially conditioned peat. At start-up, the filter bed was inoculated with four species of microorganisms. The resulting biofilter was fed with air contaminated with toluene, xylene or a mixture of toluene and xylene. The maximum elimination capacities attained were 165 g m-3 h-1 for toluene, 66 g m-3 h-1 for xylene and 115 g m-3 h-1 for the mixture of toluene and xylene. These specific performances exceed the values published in the technical and commercial literature for similar processes. Xylene isomers were degraded in decreasing order of reactivity, m-xylene, p-xylene, o-xylene. In the case of air polluted with a toluene and xylene mixture, it was noticed that the metabolism of toluene biodegradation was inhibited by the presence of xylene. Characterization of the biofilm microbial populations after several weeks of operation showed that the dominant strains among the isolated culturable strains from the biofilm, even if different from the initially inoculated strains, had at least one physiological property favoring degradation of aromatic organic rings. The performance of the biofilter was found to be dependent on the temperature of the filter media and the pressure drop through the bed. Finally, a steady state mathematical model was tested in order to theoretically describe the experimental results. This model is used to illustrate the operating diffusion and reaction regimes at steady state for the case of each pollutant. © 1998 Society of Chemical Industry
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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