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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 135 (1996), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Sequence data had indicated that cyanobacteria might possess a bidirectional hydrogenase with properties similar to the soluble enzymes from Alcaligenes eutrophus, Nocardia opaca and Desulfovibrio fructosovorans. The present study shows that extracts from the cyanobacterium Anacystis nidulans catalyse NAD(P)H-dependent H2 evolution with low but significant activity and uptake of the gas with NAD(P)+ as the electron acceptor. NAD+ is the preferred electron acceptor and NADH the preferred donor compared to NADP+ and NADPH, respectively. Activity levels of this NAD(P)+dependent, bidirectional hydrogenase are too low to support chemoautotrophic growth in A. nidulans.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 195 (2001), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Pyruvate:ferredoxin (flavodoxin) oxidoreductase (PFO, EC 1.2.7.1) catalyses the oxidative cleavage of pyruvate and coenzyme A to acetylcoenzyme A and CO2 with the simultaneous reduction of ferredoxin or flavodoxin. PFO occurs in anaerobes and in some aerobic archaea and bacteria. For cyanobacteria, activity measurements indicated the occurrence of PFO in heterocystous forms. The completely sequenced genomes of the unicellular Synechocystis sp. PCC 6803 and the heterocystous Anabaena sp. PCC 7120 and Nostoc punctiforme revealed the existence of one PFO (encoded by nifJ) in Synechocystis 6803 and N. punctiforme but two different PFOs, encoded by nifJ1 and nifJ2, in Anabaena. Sequence comparison now indicates that all cyanobacterial PFOs are more closely related to those of anaerobes than to those of aerobes. Reverse transcription-polymerase chain reaction (RT-PCR) experiments show that nifJ is transcribed in the presence of saturating iron concentrations in aerobically grown cells of the unicellular Synechococcus sp. PCC 6301 and Synechocystis 6803. Both nifJ genes are transcribed in aerobically grown Anabaena 7120. These findings are corroborated by luciferase reporter gene analysis of nifJ in Synechococcus sp. PCC 7942. The occurrence of PFO in these cyanobacteria is enigmatic.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 36 (2001), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The populations of N2-fixing and denitrifying bacteria in an acid forest soil near Cologne were characterized by gene probing. The DNA isolated from the soil for this purpose was suitable for DNA–DNA hybridization using 0.4–0.7-kb probes targeting denitrification enzymes, dinitrogenase reductase (nifH) and eubacterial 16S rRNA. The densitometrical comparison of band intensities obtained in these Southern hybridizations indicated that the highest number of total bacteria, of denitrifying and N2-fixing microorganisms always occurred in the upper (∼5 cm) soil layer. The concentration of all these organisms decreased in parallel with the soil depth. The soil investigated was rich in nitrate in all layers, and the availability of nitrate apparently did not govern the distribution of denitrifying and N2-fixing bacteria in this soil. Soil cores investigated in the laboratory formed N2O on addition of nitrate irrespective of the presence of C2H2. Hybridization intensities, with a gene probe for the 16S rRNA, and MPN numbers were generally higher in soil samples taken from the roots of plants than in the bulk soil. There was no selective enrichment of denitrifying or N2-fixing bacteria at the roots. The data obtained by hybridizing isolated soil DNA generally matched previous results obtained with culturable bacteria.
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