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Binding of the transcription factor NtcA to a part of the Nostoc punctiforme hupSL promoter region
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Physiological Botany.
Manuscript (Other academic)
URN: urn:nbn:se:uu:diva-90732OAI: oai:DiVA.org:uu-90732DiVA: diva2:163190
Available from: 2003-09-04 Created: 2003-09-04 Last updated: 2010-01-13Bibliographically approved
In thesis
1. Cyanobacterial Hydrogen Metabolism - Uptake Hydrogenase and Hydrogen Production by Nitrogenase in Filamentous Cyanobacteria
Open this publication in new window or tab >>Cyanobacterial Hydrogen Metabolism - Uptake Hydrogenase and Hydrogen Production by Nitrogenase in Filamentous Cyanobacteria
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Molecular hydrogen is a potential energy carrier for the future. Nitrogen-fixing cyanobacteria are a group of photosynthetic microorganisms with the inherent ability to produce molecular hydrogen via the enzyme complex nitrogenase. This hydrogen is not released, however, but is recaptured by the bacteria using an uptake hydrogenase. In this thesis, genes involved in cyanobacterial hydrogen metabolism were examined, and the possibility of employing genetically modified cyanobacteria for hydrogen production was investigated.

Nostoc punctiforme PCC 73102 (ATCC 29133) is a nitrogen-fixing filamentous cyanobacterium containing an uptake hydrogenase encoded by hupSL. The transcription of hupSL was characterised, and putative regulatory elements in the region upstream of the transcription start site were identified. One of these, a binding motif for the global nitrogen regulator NtcA, was further investigated by mobility shift assays, and it was found that the motif is functional in binding NtcA. Also, a set of genes involved in maturation of hydrogenases was identified in N. punctiforme, the hypFCDEAB operon. These genes were found to be situated upstream of hupSL in the opposite direction, and they were preceded by a previously unknown open reading frame, that was found to be transcribed as part of the same operon.

The potential for hydrogen production by filamentous cyanobacteria was investigated by studying mutant strains lacking an uptake hydrogenase. A mutant strain of N. punctiforme was constructed, where hupL was inactivated. It was found that cultures of this strain evolve hydrogen during nitrogen fixation. Gas exchange in the hupL- mutant and in wild type N. punctiforme was measured using a mass spectrometer, and conditions under which hydrogen production from the nitrogenase could be increased at the expense of nitrogen fixation were identified. Growth and hydrogen production in continuous cultures of a Hup- mutant of the related strain Nostoc PCC 7120 were also studied.

This thesis advances the knowledge about cyanobacterial hydrogen metabolism and opens possibilities for further development of a process for hydrogen production using filamentous cyanobacteria.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 52 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 875
Microbiology, cyanobacteria, biohydrogen, Nostoc, hydrogen production, hydrogen evolution, hydrogen metabolism, nitrogenase, hydrogenase, hydrogen, uptake hydrogenase, hupSL, hydrogen uptake mutant, uptake hydrogenase mutant, photobioreactor, hydrogenase accessory genes, hyp, transcription, RT-PCR, NtcA, mass spectrometry, heterocyst, Mikrobiologi
National Category
Microbiology in the medical area
urn:nbn:se:uu:diva-3541 (URN)91-554-5708-8 (ISBN)
Public defence
2003-09-26, the Lecture hall, room 3041, Department of Physiological Botany, Uppsala, 13:00
Available from: 2003-09-04 Created: 2003-09-04Bibliographically approved

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