Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638392
Title: Molybdenum independent nitrogenases in cyanobacteria
Author: Page, T. S.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1995
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Abstract:
Anabaena variabilis ATCC 29413, Anabaena cylindrica CCAP 1403/2A, Anabaena sp. PCC 7120, Anabaena sp. UCSB26, Microcoleus chthonoplastes and Calothrix sp. PCC 7601 appear to possess Mo-independent nitrogenases. All of these cyanobacteria grew diazotrophically in the presence of 1 mM tungstate, as well as in medium from which Mo had been carefully removed, whether or not V had been added. In growth media lacking Mo they reduced C2H2 to C2H6 as well as C2H4. Nevertheless, growth and C2H2 reduction were greatest in medium containing Mo. Nostoc sp. UCSB7, Nostoc gun UCSB31, Mastigocladus laminosus CCAP 1447/1 and Scytonema javanicum CCAP 1473/1 grew and fixed N2 in the presence of 1 mM tungstate, but did not reduce C2H2 to C2H6 in medium from which Mo had been removed. These strains are good scavengers of small traces of Mo. In cultures of Anabaena variabilis ATCC 29413, Anabaena cylindrica CCAP 1403/2A and Anabaena sp. PCC 7120, C2H2 activity recovered at a faster rate in V-medium than in Mo-medium, following incubation at low temperatures (5°C - 20°C). No evidence was provided to suggest that any of the cynobacteria studied possess a Mo-independent nitrate reductase. Anabaena variabilis ATCC 29413 and Anabaena sp. PCC 7120 grew in NO3- containing medium supplemented with V, but only at the expense of N2-fixation: C2H2 reduced to C2H6 under these conditions. Anabaena variabilis ATCC 29413, Anabaena cylindrica CCAP 1403/2A, Anabaena sp. PCC 7120 and Nostoc sp. UCSB7 grew in medium containing NO2- or NH4+ when supplemented with Mo, V or W. No C2H2 reduction was observed under any of these conditions. Growth rates were significantly slower in the presence of NH4+ than on N2, NO3- or NO2-. Isolation of the V-nitrogenase from Clostridium pasteurianum was performed using an S-200 gel filtration column. EPR studies have shown that the component 1 protein of this enzyme possesses both FeMoco and FeVaco. The C2H2 reduction pattern is indicative of a Mo-independent system.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.638392  DOI: Not available
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