Coordination of Carbon Dioxide and Nitrogen Metabolism in Rhodobacter sphaeroides

Studies of metabolism usually characterize a system in isolation without a whole-cell focus on interactions with other metabolic pathways. In this work, two different metabolic pathways of the nonsulfur purple bacterium <i>Rhodobacter sphaeroides</i> were studied simultaneously <i>in vivo</i> to determine their influence upon each other. <i>Rb. sphaeroides</i> is capable of nitrogen fixation via nitrogenase catalysis and carbon dioxide fixation via the Calvin-Benson-Bassham (CBB) cycle. When the CBB cycle was inactivated through gene deletions, strains developed that deregulated nitrogenase. Genomic sequencing and comparative analyses of these mutant strains revealed multiple mutations that could account for the nitrogenase active phenotype. A mutation in the gene that encodes for glutamine synthetase and another in the gene that encodes for one subunit of nitrogenase were shown be sufficient to derepress nitrogenase synthesis and to affect its activity, respectively. Further studies of nitrogenase regulation led to the observation that the N-terminal GAF domain of the transcriptional regulator of nitrogenase, NifA, contributed to its post-translational response to cellular nitrogen status. Finally, the reciprocal response of the CBB cycle to nitrogenase activity was investigated determining that the expression of the genes of the CBB cycle was repressed when nitrogenase was active. The CBB enzyme phosphoribulokinase was found to mediate this repression. This study thus explored the coordination of carbon dioxide and nitrogen metabolism in <i>Rb. sphaeroides</i>.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Microbiology

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Farmer, Ryan Michael

Contributors dc:contributor

• Tabita, F. Robert

• Microbiology
• Rhodobacter sphaeroides
• metabolism
• nitrogenase
• CBB cycle

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1365519943

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1365519943