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  • 1
    Electronic Resource
    Electronic Resource
    Structural analysis of the Trichodesmium nitrogenase iron protein: implications for aerobic nitrogen fixation activity (1997)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 153 (1997), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Trichodesmium spp. are marine filamentous nitrogen-fixing cyanobacteria which play an important role in the nitrogen budget of the open ocean. Trichodesmium is unique in that it is nonheterocystous and fixes nitrogen during the day, while evolving oxygen through photosynthesis, even though nitrogenase is sensitive to oxygen inactivation. The sequence of the gene encoding the Fe protein component of nitrogenase from the recently cultivated isolate Trichodesmium sp. IMS 101 was used to construct a 3-dimensional model of the Fe protein, by comparison to the X-ray crystallographic structure of the Fe protein of the γ-proteobacterium Azotobacter vinelandii. The primary differences in amino acid sequences of the Fe protein from diverse organisms do not impact the critical structural features of the Fe protein. It can be concluded that aerobic nitrogen fixation in Trichodesmium spp. is not facilitated by unique structural features of Trichodesmium Fe protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1997.tb12589.x
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  • 2
    Electronic Resource
    Electronic Resource
    Diel variability in transcription of the structural gene for glutamine synthetase (glnA) in natural populations of the marine diazotrophic cyanobacterium Trichodesmium thiebautii (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 21 (1996), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: A 360-bp fragment of the Trichodesmium thiebautii glutamine synthetase gene (glnA) was amplified from DNA isolated from oceanic populations of this ecologically important, diazotrophic cyanobacterium. The cloned fragment showed high homology to the type 1 glutamine synthetase (GS) enzymes of other cyanobacteria and was used to probe the in situ, temporal variability in transcription of Trichodesmium GS. Three distinct phases in the diel pattern of glnA mRNA abundance were observed. These appear to be correlated with the temporal variability in carbon and nitrogen fixation rates and the effect that these physiological processes have on the size of cellular pools of the primary end-products of N assimilation. Our data show that Trichodesmium thiebautii GS is regulated at the level of transcription and support the hypothesis that GS expression in this organism is subject to similar controls as those established for heterocyst-forming cyanobacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1996.tb00346.x
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  • 3
    Electronic Resource
    Electronic Resource
    Are Recent Watershed Disturbances Associated with Temporal and Spatial Changes in Water Quality of Lake George, New York, USA? (1997)
    Springer
    Environmental management 21 (1997), S. 725-732 
    Details
    ISSN: 1432-1009
    Keywords: KEY WORDS: Repeated-measures ANOVA; Split-plot design; Lakewater chemistry; Lake George
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: a (Chl a), silica (Si), and chloride (Cl) through the use of proper statistical techniques. Results indicate no statistically significant changes in the concentrations of TP, Chl a, or Si in the spring or summer from 1981 to 1993. A significant temporal trend of increase in Cl concentration is, however, detected. This is perhaps the strongest evidence that the development of the Lake George watershed has affected lakewater chemistry. In spring, the concentrations of TP, Chl a, Si, and Cl, averaged over all 13 years, were higher in the south basin, but differences are not statistically significant (i.e., P 〉 0.05). In summer, Si was slightly but significantly lower, and Cl was nonsignificantly higher in the south basin. Significant interactions between temporal and spatial changes are detected based only on summer values of TP and Chl a, indicating differential trends of change for these two variables in the south and north basins during the last 13 years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002679900062
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  • 4
    Electronic Resource
    Electronic Resource
    Expression of photosynthesis genes in relation to nitrogen fixation in the diazotrophic filamentous nonheterocystous cyanobacterium Trichodesmium sp. IMS 101 (1999)
    Springer
    Plant molecular biology 41 (1999), S. 89-104 
    Details
    ISSN: 1573-5028
    Keywords: cyanobacteria ; circadian rhythm ; psaA ; psbA ; Trichodesmium sp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The daily cycle of nitrogenase expression in the marine filamentous nonheterocystous cyanobacterium Trichodesmium spp. is controlled by a circadian rhythm. We evaluated the rhythm of two key photosynthesis genes, psbA of photosystem II and psaA of photosystem I, in Trichodesmium sp. IMS 101 using the 3 criteria for an endogenous rhythm. The transcript abundance of psbA and psaA transcripts oscillated with a period of ca. 24 h under a 12 h light/12 h dark regime. At 24 °C and 28 °C the cyclic pattern of transcript abundance was maintained for at least 58 h under constant light conditions, whereas the periods were about 24 h at 24 °C, and 26–30 h at the higher temperature. The cycles of psbA and psaA gene expression were entrained using light-dark cues. Transcription of nifHDK was initiated prior to the light period, followed by psbA and finally psaA. There was a 90° (6 h) phase difference between the net accumulation of nifHDK and psbA transcripts, as well as between that of psbA and psaA transcripts. Results of inhibitor experiments indicated that psbA and psaA transcription was regulated differently by initiation and degradation during the light period. Short-term changes of light conditions resulted in significant effects on psbA transcription and nitrogenase activity, but had less of an effect on psaA and nifHDK transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006231805030
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  • 5
    Electronic Resource
    Electronic Resource
    Determinants of Summer Nitrate Concentration in a Set of Adirondack Lakes, New York (1999)
    Springer
    Water, air & soil pollution 111 (1999), S. 19-28 
    Details
    ISSN: 1573-2932
    Keywords: Adirondack region ; canonical discriminant analysis ; cluster analysis ; lake nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Following reductions in the emission and deposition of sulfur compounds in the past decade, atmospheric deposition of nitrogen has become a focus of concern. Identification of watershed characteristics that mediate the effect of atmospheric nitrogen deposition can help evaluate the sensitivity of lakes to chronic and episodic nitrogen addition. Twenty four lakes in the southwestern portion of the Adirondack Park, New York, U.S.A., were classified into three N classes by cluster analysis of lakewater NO3- N concentration [N] during the summers of 1994–1996. The lake-N classes were best characterized as having (1) low [N] throughout the summer, (2) high [N] in early- but low [N] in late-summer, and (3) high [N] throughout the summer. The three lake-N classes were reconstructed perfectly by canonical discriminant analysis based mainly on lake average depth (AD), and lakewater concentrations of chlorophyll a [Chla] and SO4-S [S] in mid-summer. Increases in AD and [S], but decrease in [Chla] corresponded with a transition from low- to high-N classes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005006108629
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