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  • 1
    Electronic Resource
    Electronic Resource
    Cultivation of hyperthermophilic archaea in capillary tubes resulting in improved preservation of fine structures (1997)
    Springer
    Archives of microbiology 168 (1997), S. 373-379 
    Details
    ISSN: 1432-072X
    Keywords: Key words Hyperthermophilic archaea ; Cultivation ; Cellulose capillary tubes ; Cryo-fixation ; Freeze-substitution ; Cell-to-cell connection ; Pyrodictium ; Thermoproteus ; Pyrobaculum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method for cultivating hyperthermophilic archaea that results in very high cell densities and in improved structural preservation of the cells is described. Cellulose capillary tubes, originally introduced as containers for embedding for electron microscopy, were filled with cells, closed at both ends, and put into sterile culture medium. Within these capillaries, which serve as ultrafiltration chambers, cells could be cultivated to much higher cell densities than in regular cultures. The capillaries containing cells were processed for ultrathin-sectioning by fixation, freeze-substitution, and embedding. Using this cultivation procedure, centrifugation, which may destroy sensitive structural components, could be avoided, and the cells of hyperthermophilic archaea were well-preserved. These undisturbed cells revealed the following new structural features: (1) a high number of tubules in ultrathin-sections, indicating a well-preserved network of Pyrodictium cells and tubules; (2) “ultraflat areas” of Pyrodictium cells, with the two membranes being in direct contact and, at some places, bulging out, forming evaginations; (3) novel cell-to-cell connections between Thermoproteus cells and, similarly, between Pyrobaculum cells; and (4) a surface coat on Pyrobaculum aerophilum cells. The cultivation procedure offers distinct advantages over conventional techniques and might be applicable for improved electron microscopy of other sensitive microorganisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050511
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  • 2
    Electronic Resource
    Electronic Resource
    The malonate decarboxylase enzyme system of Malonomonas rubra: evidence for the cytoplasmic location of the biotin-containing component (1993)
    Springer
    Archives of microbiology 160 (1993), S. 126-131 
    Details
    ISSN: 1432-072X
    Keywords: Malonomonas rubra ; Propionigenium modestum ; Malonate decarboxylase ; Methylmalonyl-CoA decarboxylase ; Biotin ; Avidin ; Electron microscopy ; High pressure freezing ; Immunolabeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Malonate decarboxylase of Malonomonas rubra is a complex enzyme system involving cytoplasmic and membrane-bound components. One of these is a biotin-containing protein of Mr 120'000, the location of which in the cytoplasm was deduced from the following criteria: (i) If the cytoplasm was incubated with avidin and the malonate decarboxylase subsequently completed with the membrane fraction the decarboxylase activity was abolished. The corresponding incubation of the membrane with avidin, however, was without effect. (ii) Western blot analysis identified the single biotin-containing polypeptide of Mr 120'000 within the cytoplasm. (iii) Transmission electron micrographs of immuno-gold labeled M. rubra cells clearly showed the location of the biotinyl protein within the cytoplasm, whereas the same procedure with Propionigenium modestum cells indicated the location of the biotin enzyme methylmalonyl-CoA decarboxylase in the cell membrane. The biotin-containing protein of the M. rubra malonate decarboxylase enzyme system was not retained by monomeric avidin-Sepharose columns but could be isolated with this column in a catalytically inactive form in the presence of detergents. If the high binding affinity of tetrameric avidin towards biotin was reduced by destructing part of the tryptophan residues by irradiation or oxidation with periodate, the inhibition of malonate decarboxylase by the modified avidin was partially reversed with an excess of biotin. Attempts to purify the biotin protein in its catalytically active state using modified avidin columns were without success.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288714
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  • 3
    Electronic Resource
    Electronic Resource
    The lytic enzyme in bacteriophage ψM1-induced lysates of Methanobacterium thermoautotrophicum Marburg (1992)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 100 (1992), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The lytic enzyme from bacteriophage ψM1-induced lysates of Methanobacterium thermoautotrophicum was purified approx. 80-fold to near electrophoretic homogeneity. It was a 31-kDa monomeric, oxygen-sensitive pseudomurein endopeptidase hydrolysing the ?-Ala-Lys bond of pseudomurein. Pseudomurein endopeptidase-specific polyclonal antibodies reacted with a 31-kDa protein in crude extracts of non-infected host cells. This cross-reacting protein was purified. It did not exhibit lytic activity but its N-terminus was identical with the N-terminus of pseudomurein endopeptidase. The 31-kDa protein thus probably represents a pseudomurein endopeptidase whose autolytic activity is under control in non-infected, but deregulated in phage ψM1-infected cells. Its preferential location in the cell-wall area was demonstrated by immuno-electron microscopy and argued for a role of pseudomurein endopeptidase in the expansion of the cell wall during growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1992.tb14073.x
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  • 4
    Electronic Resource
    Electronic Resource
    Cellular localisation by immunolabelling and transmission electron microscopy of oxaloacetate decarboxylase or its individual subunits synthesised in Escherichia coli (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 136 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The genes oadGAB encoding the oxaloacetate decarboxylase γ, α and β-subunits from Klebsiella pneumoniae were expressed in Escherichia coli. Using different expression vectors, the entire enzyme or its individual subunits were synthesised. The expression was evidenced immunologically in whole cells with polyclonal antibodies raised against the purified oxaloacetate decarboxylase. The expressed α-subunit or a combination of a and β-subunits were shown to reside in the cytoplasm, while the entire oxaloacetate decarboxylase or a γα-complex were located mostly in the cytoplasmic membrane. Interestingly, overexpression of the γα-complex or the entire oxaloacetate decarboxylase in E. coli led to a significant immunogold labelling in the cytoplasm, indicating that the a-subunit was not completely complexed to the membrane-bound γ or βγ-subunits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08021.x
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  • 5
    Electronic Resource
    Electronic Resource
    Immunogold labeling in scanning electron microscopy (1996)
    Springer
    Histochemistry and cell biology 106 (1996), S. 31-39 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004180050021
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  • 6
    Electronic Resource
    Electronic Resource
    Microbes, enzymes and genes involved in dichloromethane utilization (1994)
    Springer
    Biodegradation 5 (1994), S. 237-248 
    Details
    ISSN: 1572-9729
    Keywords: Dichloromethane ; dichloromethane dehalogenase ; glutathione S-transferase ; methylotrophic bacteria ; Methylobacterium sp. ; Methylophilus sp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Dichloromethane (DCM) is efficiently utilized as a carbon and energy source by aerobic, Gram-negative, facultative methylotrophic bacteria. It also serves as a sole carbon and energy source for a nitrate-respiringHyphomicrobium sp. and for a strictly anaerobic co-culture of a DCM-fermenting bacterium and an acetogen. The first step of DCM utilization by methylotrophs is catalyzed by DCM dehalogenase which, in a glutathione-dependent substitution reaction, forms inorganic chloride and S-chloromethyl glutathione. This unstable intermediate decomposes to glutathione, inorganic chloride and formaldehyde, a central metabolite of methylotrophic growth. Genetic studies on DCM utilization are beginning to shed some light on questions pertaining to the evolution of DCM dehalogenases and on the regulation of DCM dehalogenase expression. DCM dehalogenase belongs to the glutathione S-transferase supergene family. Analysis of the amino acid sequences of two bacterial DCM dehalogenases reveals 56% identity, and comparison of these sequences to those of glutathione S-transferases indicates a closer relationship to class Theta eukaryotic glutathione S-transferases than to a number of bacterial glutathione S-transferases whose sequences have recently become available.dcmA, the structural gene of the highly substrate-inducible DCM dehalogenase, is carried in most DCM utilizing methylotrophs on large plasmids. InMethylobacterium sp. DM4 its expression is governed bydcmR, a regulatory gene located upstream ofdcmA. dcmR encodes atrans-acting factor which negatively controls DCM dehalogenase formation at the transcriptional level. Our working model thus assumes that thedcmR product is a repressor which, in the absence of DCM, binds to the promoter region ofdcmA and thereby inhibits initiation of transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00696462
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  • 7
    Electronic Resource
    Electronic Resource
    Isolation of an anaerobic bacterium which reductively dechlorinates tetrachloroethene and trichloroethene (1996)
    Springer
    Biodegradation 7 (1996), S. 507-511 
    Details
    ISSN: 1572-9729
    Keywords: anaerobic respiration ; Dehalobacter restrictus ; reductive dehalogenation ; 16S rRNA sequence ; tetrachloroethene ; trichloroethene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Strain TEA, a strictly anaerobic, motile rod with one to four lateral flagella and a crystalline surface layer was isolated from a mixed culture that completely reduces chlorinated ethenes to ethene. The organism coupled reductive dehalogenation of tetrachloroethene or trichloroethene to cis-1,2-dichloroethene to growth, using molecular hydrogen as the electron donor. It was unable to grow fermentatively or in the presence of tri- or tetrachloroethene with glucose, pyruvate, lactate, acetate or formate. The 16S rDNA sequence of strain TEA was 99.7% identical to that of Dehalobacter restrictus. The two organisms thus are representatives of the same species or the same genus within the Bacillus/Clostridium subphylum of the gram-positive bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00115297
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  • 8
    Electronic Resource
    Electronic Resource
    High resolution biological scanning electron microscopy: A comparative study of low temperature metal coating techniques (1991)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 18 (1991), S. 440-449 
    Details
    ISSN: 0741-0581
    Keywords: High resolution SEM ; Cryomethods ; Double-axis rotary shadowing ; Unidirectional shadowing ; Planar-magnetron sputtering ; Chromium ; Platinum/carbon ; T4 phages ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Structural information on the surface of biological specimens can be resolved within molecular dimensions by “in-lens” field emission scanning electron microscopes when cryo-methods are used to adequately preserve the native state of the specimen. The visual definition of molecular surface structures depends largely on the metal coating. The thickness of the coating, as well as the temperature at which it is deposited, are among the most important parameters affecting visual definition. These were evaluated on T4 polyheads and T4D phages using chromium double-axis rotary shadowing (DARS). Micrographs of optimally DARS coated T4 polyheads and T4D phages were compared with chromium planar-magnetron sputtering (PMS) and unidirectional shadowing with platinum/carbon. Metal deposition was carried out at low temperatures during all three procedures.Optimal visual definition of structural details on the surface of DARS coated T4 polyheads and T4D phages (capsomeres of T4 polyheads and their subunits with diameters of 8 and 3 nm; T4D phage tail fibres with a thickness of 3 nm) is achieved at a thickness of the chromium film greater than the minimum required for metal film coalescence. Chromium DARS coating at room temperature resulted in poor structural definition, whereas DARS at specimen temperatures of -85°C and -150°C, with the chromium thickness optimized for each temperature, yielded good visual detail of polyhead substructures. The visual definition was slightly reduced when DARS coating was carried out at a specimen temperature of -250°C. Adequate structural visibility of T4D phage and T4 polyhead surface structures was achieved with the three coating techniques tested. Smaller filamentous structures, however (e.g., phage tail fibres), were more clearly identified after chromium DARS coating or unidirectional platinum/carbon shadowing than after optimized PMS with chromium. Each method has its own merits.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060180414
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  • 9
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    Graft Polymerization of Styrene on Mica:  Formation and Behavior of Molecular Droplets and Thin Films (1999)
    American Chemical Society
    Details
    Publication Date: 1999-09-01
    Print ISSN: 0743-7463
    Electronic ISSN: 1520-5827
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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  • 10
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    Cultivation of hyperthermophilic archaea in capillary tubes resulting in improved preservation of fine structures (1997)
    Springer
    Details
    Publication Date: 1997-10-15
    Print ISSN: 0302-8933
    Electronic ISSN: 1432-072X
    Topics: Biology
    Published by Springer
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