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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Proteinaceous, hair-like appendages known as fimbriae or pili commonly extend from the surface of prokaryotic cells and serve important functions such as cell adhesion, biofilm formation, motility and DNA transfer. Here we show that a novel group of archaea from cold, sulphidic springs has developed cell surface appendages of an unexpectedly high complexity with a well-defined base-to-top organization. It represents a new class of filamentous cell appendages, for which the term ‘hamus’ is proposed. Each archaeal cell is surrounded by a halo of about 100 hami, which mediate strong adhesion of the cells to surfaces of different chemical composition. The hami are mainly composed of 120 kDa subunits and remained stable in a broad temperature and pH range (0–70°C; 0.5–11.5). Electron microscopy and cryo-electron tomography revealed that the hamus filament possesses a helical basic structure. At periodic distances, three prickles emanate from the filament, giving it the character of industrially produced barbwire. At its distal end the hami carry a tripartite, barbed grappling hook (60 nm in diameter). The architecture of this molecular hook is reminiscent of man-made fishhooks, grapples and anchors. It appears that nature has developed a perfect mechanical nano-tool in the course of biological evolution, which also might prove useful in the field of nanobiotechnology.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 218 (2003), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A variant of Archaeoglobus fulgidus VC-16 was isolated from cultures obtained after a stepwise transfer from media containing 1.8–6.3% NaCl by a plating-independent, selected-cell cultivation technique, using a laser microscope. This variant, A. fulgidus VC-16S, had a higher growth rate throughout the salt range of the parental strain, but was also able to grow in media containing NaCl up to 6.3%, whereas the parental strain could not grow above 4.5% NaCl. Diglycerol phosphate (DGP), only encountered in the Archaeoglobales, was the major solute accumulated under supra-optimal salinities, whereas at supra-optimal growth temperatures di-myo-inositol phosphate was the predominant solute. The accumulation of compatible solutes during growth of variant VC-16S was lower than in the parental strain within 1.8–4.5% NaCl, but the levels of compatible solutes, including DGP, increased sharply in the variant at higher salinities (5.5 and 6.0%). This variant represents, at this time, one of the most halophilic hyperthermophiles known, and its ability to grow at high salinity appears to be due to the massive accumulation of DGP.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 148 (1997), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Fluorescent dyes were assessed with regard to their ability to discriminate between viable and non-viable cells of hyperthermophilic archaea and bacteria. Using bis-(1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC4(3)), a membrane potential-sensitive probe, a safe and rapid discrimination of viable cells was possible by fluorescence microscopy. Single viable individuals, identified by DiBAC4(3), were selectively isolated from mixtures of viable and dead cells by the use of a laser microscope (`optical tweezers') and grown in pure culture.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 226 (2003), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Coproporphyrinogen-III oxidase (CPO) catalyses the conversion of coproporphyrinogen-III to protoporphyrinogen-IX in the haem biosynthetic pathway, and its deficient activity is associated with human hereditary coproporphyria. The 47% sequence identity between the oxygen-dependent CPO from Escherichia coli and its human counterpart makes the bacterial enzyme a good model system for structural studies of this disease. Therefore, we overexpressed and purified to homogeneity the oxygen-dependent CPO from E. coli and its selenomethionine derivative fused with a His6-tag. Both preparations showed a specific activity of 37 500 U mg−1, had a subunit molecular mass of 35 kDa and behaved as a compact shaped dimer. First crystallisation trials produced plate-shaped diffracting crystals.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Recently, a unique microbial community, growing in a whitish, macroscopically visible strings-of-pearls-like structure was discovered in the cold, sulfidic marsh water of the Sippenauer Moor near Regensburg, Bavaria, Germany. The pearls interior is predominated by microcolonies of the non-methanogenic SM1 euryarchaeon; the outer part of the pearls is mainly composed of Thiothrix. To screen sulfidic ecosystems for the distribution of such unique microbial communities, comparative microbial and geochemical analyses of cold, sulfidic springs of three geographically distinct locations in Bavaria, Germany, and Dalyan, Turkey, were performed. Here, we report on the discovery and study of another type of strings-of-pearls revealing a new microbial community structure. While the SM1 euryarchaeon is again the predominant archaeal constituent, the bacterial partner is the so-called IMB1 η-proteobacterium. Due to the predominance of the IMB1 η-proteobacterium, the strings-of-pearls reveal a fluffy and greyish macroscopical appearance. The phylogenetic survey revealed SM1 euryarchaeal relatives, designated as SM1 group, in all sites studied, indicating a widespread distribution of these archaea in terrestrial ecosystems.
    Type of Medium: Electronic Resource
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