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Mutational analysis of the Rhodobacter Capsulates ORF162B gene

University of British Columbia

There are several open reading frames (orfs) of unknown function in the photosynthesis gene cluster of Rhodobacter capsulatus. It is possible that these orfs, including orfl62b, have a function in bacterial photosynthesis. When R. capsulatus RNA was probed for the presence of an orfl62b transcript, a 4 kb polycistronic mRNA was detected. Strains were then created which possessed either a polar or non-polar deletion mutation of orfl62b. These mutant strains were evaluated on the basis of their light harvesting (LH) and reaction center (RC) complex levels, chromatophore protein band intensities and their ability to grow photosynthetically. Mutants were complemented with orfl62b in trans. In a non-polar mutant orfl62b strain, decreases in LH and RC complex levels as well as photosynthetic growth rate were restored by trans complementation. When a polar mutation was inserted into orfl 62b such that any downstream orfs cotranscribed with 162b would no longer be expressed, a reduction in LH and RC complex levels as well as photosynthetic growth rate was observed. As with the non-polar mutation, the LH and RC complex levels were increased upon trans complementation with orfl62b, whereas the wild type generation time was not restored. It is concluded that orfl62b and at least one orf found downstream of, and cotranscribed with, orfl62b are genes that encode proteins which are involved in bacterial photosynthesis. A hypothesis that orfl62b functions in the assembly or interaction of complexes is proposed.

Thesis/Dissertation

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2009-05-04

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http://hdl.handle.net/2429/7818

Microbiology and Immunology

University of British Columbia

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