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  • 1
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Immobilized cells ; Gene expression ; Regulon ; nifH protein ; Desiccation ; Nostoc commune
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two-dimensional gel electrophoresis was used to analyze the effects of water stress (immobilization and rapid drying, desiccation, rewetting) on the protein index of the desiccation-tolerant cyanobacteriumNostoc commune UTEX 584. Five major “landmark” protein constellations were detected in the protein index of control cells (in liquid culture) and were designated A (1 protein), B (7 proteins), C (8 proteins), D (3 proteins) and E (2 proteins). These included proteins which showed different sensitivities to water stress. Upon immobilization and rapid drying of the cells at a water potential ({ie87-1}) of -99.5 MPa (aw=0.5) for 30 min, few changes took place in the index. Four conspicuous proteins and the majority of proteins in the size range 18 to 97 K diminished in abundance while most proteins of constellations A, B and C were detected in fluorographs with the same intensity as in the control. Although protein synthesis continued during this time of drying, no novel class of proteins was detected. The level of incorporation of35S in protein increased rapidly during the first 60 min of rehydration, and then decreased gradually for a further 2.5 h. Extant proteins that were hardly detectable after 24 h of drying, reappeared and increased in abundance upon rewetting of cells for 60 min while a number of proteins which disappeared after drying did not appear during this time. No novel class of proteins appeared upon rewetting. During further rehydration, extensive proteolysis was observed. ThenifH product (Fe protein of nitrogenase) was detected on Western blots — through cross-reaction with antibody — as an acidic polypeptide with a molecular mass of 33.8 K. Fe-protein was detected in immobilized cells after 30 min of drying, in desiccated material, and in rehydrated cells.
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  • 3
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Chroococcidiopsis ; Chroococcus ; Water stress ; Photosynthesis ; Endolithic ; Matric ; Osmotic ; Taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four strains of Chroococcidiopsis and one Chroococcus, all isolated from extreme arid desert rocks, and one marine Chroococcus, were subjected to water stress using both matric and osmotic control methods. For all Chroococcidiopsis strains, photosynthetic rates decreased with decreasing water potential. After 24h preincubation the decrease was linear but after 72h there was a sharp drop below-3400 kPa (a w≏0.976). In contrast, the two Chroococcus strains showed optimum photosynthesis between-3000 and-4000 KPa. It appears, therefore, that Chroococcidiopsis in deserts may have a different survival strategy in response to aridity than Chroococcus (rare in deserts). Absolute rates of 14CO2 uptake were higher in matric than in osmotic control systems. It is suggested that, in a matric experimental system, the water status is more representative of the natural conditions in arid environments. The consistent differences between different strains in their response to water stress suggest that this character in Cyanobacteria may be of taxonomic significance.
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  • 4
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Immobilised cells ; Desiccation ; Water stress ; Nitrogenase ; ATP pool ; Photooxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cells of Nostoc commune UTEX 584 from liquid cultures expressed an upshift in nitrogenase activity when immobilised on inert supports and exposed to matric water potentials between -1.10 and -99.5 MPa. Cells incubated at 0.10 MPa (aw=c 1.0) maintained increased activity for at least 48 h following immobilization. At water potentials below -23.1 MPa (aw=0.85), the upshift was transitory. Nitrogenase activity decreased rapidly when immobilised cells were incubated at lower values of ψm. Desiccated cells stored at -99.5 MPa (aw=0.50) underwent an upshift in nitrogenase activity, and in the size of the intracellular ATP pool, when rewetted with either distilled water or liquid MBo medium (ψo =-0.18 MPa). The upshift in nitrogenase activity was chloramphenicol-sensitive and was preceeded by a lag. The duration of the lag depended on the time taken to equilibrate cells to-99.5 MPa, the time desiccated, and the conditions of storage and rewetting. Cells that had no, or very low, nitrogenase activity when rewetted in air, showed a marked stimulation of nitrogenase activity in the presence of 5% v/v CO2 under both aerobic and anerobic conditions. When rewetted in the presence of 1% w/v glucose (ψo =-0.14 MPa), vegetative cells remained intact, but heterocysts underwent autolysis and nitrogenase activity was not detected, even in the presence of 5% v/v CO2.
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 335 (1988), S. 679-682 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] DURING the course of human evolution breast feeding has come to play a key role in regulating both the mother's fertility and the infant's wellbeing, and we tamper with it at our peril. The contraceptive effect of breast feeding has been recognized since antiquity. Aristotle1 pointed out that ...
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 97 (1996), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The cyanobacterium Nostoc commune has been developed as the prokaryotic model for the anhydrobiotic cell and it provides the means to answer fundamental questions about desiccation tolerance. The anhydrobiotic cell is characterized by its singular lack of water — with contents as low as 0.02 g H2O g-1 dry weight. These levels are orders of magnitude lower than those found either in bacterial spores or in cells subjected to acute salt (osmotic) stress. Mechanisms that contribute to the desiccation tolerance of N. commune include the selective stabilization of anhydrous proteins, the secretion of water- and lipid-soluble UV-absorbing pigments, and the secretion of a complex glycan that immobilizes the cells, immobilizes water stress proteins and the UV-absorbing pigments, and which may confer the properties of a mechanical glass upon colonies. Rehydration of desiccated cells induces an instantaneous resumption of metabolic activities, including membrane transport and global lipid biosynthesis. These initial recoveries may not follow classical Arrhenius-based kinetics. The rehydrating cell exhibits a stringent, stepwise recovery of physiological capacities beginning with respiration, then photosynthesis and finally nitrogen fixation. Protein turnover, de novo protein synthesis and a rapid rise in the intracellular ATP pool accompany these recoveries. During the early stages of rehydration, the de novo transcription of one gene set (rpoC1C2) is achieved using an extant DNA-dependent RNA polymerase holoenzyme that remains stable in desiccated cells. These properties of desiccation-tolerant cyanobacleria, present in extant forms such as N. commune and Chroococcidiopsis spp., may have been utilized by the eoanhydrobiotes. However, it is the desiccation-tolerant cyanobacterium as a whole, and not some collection of disparate properties, that must be considered as the primary strategy for the achievement of desiccation tolerance.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 41 (1987), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two microscale methods were developed to isolate and analyze the [2-14C]uracil-labeled nucleic acids of immobilized, dried cells of the desiccation-tolerant cyanobacterium Nostoc commune UTEX584. The incidence of single-strand breaks (‘nicks’) in DNA of light-desiccated, but not dark-desiccated cells, was demonstrated by the use of DNA modification enzymes.
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  • 8
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Three simple methods are described that permit cells of cyanobacteria, immobilised on filter supports, to be subjected to matric water stress that leads to a downshift in nitrogenase activity. In Nostoc commune, a desiccation-tolerant form, nitrogenase activity is more sensitive to water stress than the intracellular ATP pool. When it is dried rapidly to −99.5 MPa, nitrogenase activity ceases within 30 min while the ATP pool is maintained at 16.07 pmol ATP ·μg protein−1. During short-term incubation, decreasing ψm from −0.10 to −23.1 MPa may result in an increased rate of CO2 uptake.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 24 (1984), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The distribution of plasmid DNA has been studied in 23 strains and variants of non-heterocystous filamentous cyanobacteria that are susceptible to infection by the LPP-1 cyanophage (archetype). 21 have identical plasmid profiles and contain 3 plasmids of Mrs 0.9, 10 and approx. 12 · 106 respectively. In one strain, Plectonema FS180, the plasmids have been designated pMP1, pMP2, and pMP3, respectively. pMP1 shows sequence homology with pMP2 and pMP3 but not with DNA from an LPP-type cyanophage. Plectonema UTEX 598 lacks the small plasmid only, while Plectonema UTEX 1541 is distinct amongst all these strains with 3 plasmids of Mrs 3, 10, and 〉 30 · 106, respectively. The findings support the view that the majority of these strains may be independent isolates of a single species.
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  • 10
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Inspection of the genomes for the bacteria Bacillus subtilis 168, Borrelia burgdorferi B31, Escherichia coli K-12, Haemophilus influenzae KW20, Helicobacter pylori 26695, Mycoplasma genitalium G-37, and Synechocystis sp PCC 6803 and for the archaeons Archaeoglobus fulgidus VC-16 DSM4304, Methanobacterium thermoautotrophicum delta H, and Methanococcus jannaschii DSM2661 revealed that each contains at least one ORF whose predicted product displays sequence features characteristic of eukaryote-like protein-serine/threonine/tyrosine kinases and protein-serine/threonine/tyrosine phosphatases. Orthologs for all four major protein phosphatase families (PPP, PPM, conventional PTP, and low molecular weight PTP) were present in the bacteria surveyed, but not all strains contained all types. The three archaeons surveyed lacked recognizable homologs of the PPM family of eukaryotic protein-serine/threonine phosphatases; and only two prokaryotes were found to contain ORFs for potential protein phosphatases from all four major families. Intriguingly, our searches revealed a potential ancestral link between the catalytic subunits of microbial arsenate reductases and the protein-tyrosine phosphatases; they share similar ligands (arsenate versus phosphate) and features of their catalytic mechanism (formation of arseno- versus phospho-cysteinyl intermediates). It appears that all prokaryotic organisms, at one time, contained the genetic information necessary to construct protein phosphorylation–dephosphorylation networks that target serine, threonine, and/or tyrosine residues on proteins. However, the potential for functional redundancy among the four protein phosphatase families has led many prokaryotic organisms to discard one, two, or three of the four.
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