In this study, we report that expression of the ๐ข๐ณ๐จ๐๐๐ operon is induced in stationary phase cultures and that this increase is largely dependent on RpoS, the alternative stress sigma factor. Using combinatorial ๐ข๐ณ๐จ๐ and ๐ณ๐ฑ๐ฐ๐ mutants, we evaluated the relative contributions of these two regulators to the expression of ๐ข๐ณ๐จ๐ using operon ๐ญ๐ข๐ค๐ก fusions. While ArgR was found to be the main factor responsible for de-repression of the ๐ข๐ณ๐จ๐๐๐ operon, RpoS was required for full expression of this biosynthetic operon at concentrations below 10 ฮผg arginine mlโปยน, a level at which growth of an arginine auxotroph was arginine limited. At high arginine concentrations (>10 ฮผg mlโปยน) ๐ข๐ณ๐จ๐๐๐ expression was strongly repressed as expected by ArgR. ๐ข๐ณ๐จ๐๐๐ expression was 30 fold higher in ฮ๐ข๐ณ๐จ๐ mutants relative to a wild type fully repressed strain and this expression was independent of RpoS. These results indicate that RpoS plays an important role in the regulation of arginine biosynthesis, particularly when the operon is partially de-repressed as would be the case in starvation conditions. / Thesis / Master of Science (MS)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22925 |
| Date | 09 1900 |
| Creators | Weerasinghe, Jeevaka |
| Contributors | Schellhorn, Herb, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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