For organisms such as Rhodobacter sphaeroides osmoadaptation is essential to survival, since it encounters changes in salinity in its natural habitat of brackish waters. Because it is metabolically versatile, it serves as a useful model in examining how regulatory features of osmoadaptation are integrated into the regulatory circuits that provide the cell with the means to switch from one metabolic option to another. Known components of osmoadaptation in R. sphaeroides include the transport or synthesis of compatible compounds and alterations in fatty acid and phospholipid composition of the cell membrane. However, the transcriptional regulation of the genes associated with these adaptations has not been unraveled. The R. sphaeroides crpO gene has been found to increase NaCl tolerance when present in multicopy. Towards evaluating the role of crpO in NaCl tolerance, strains with different levels of functional CrpO protein were constructed and characterized with respect to each component of osmoadaptation. The main findings are (1) crpO is an essential gene, (2) improved NaCl tolerance by increasing crpO gene dosage is not due to altered compatible solute synthesis or transport; rather (3) fatty acid and phospholipid, especially cardiolipin, composition and quantity are altered in cells with multiple copies of crpO. The importance of this work is its contribution towards understanding the regulatory events associated with osmoadaptation in an organism that is capable of many different energy metabolisms including both aerobic and anaerobic respirations and also anoxygenic photosynthesis. Improved knowledge of how this happens in R. sphaeroides has the potential to increase our understanding for other organisms having the same individual and combined metabolic capabilities.
|Commitee:||Larsen, Raymond, Rogers, Scott|
|School:||Bowling Green State University|
|School Location:||United States -- Ohio|
|Source:||MAI 57/05M(E), Masters Abstracts International|
|Keywords:||Gene regulation, Osmoadaptation, Osmoregulation, Rhodobacter sphaeroides|
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