Escherichia coli survives in both nutrient rich nutrient-limited environments. As such, understanding the gene and protein level activity that occurs during stationary phase is considered an important aspect of bacterial survival. Escherichia coli has been studied for decades providing substantial insight into gene expression profiles in exponential phase and recently, during adaptation to stationary phase. This led to the discovery of RpoS as a growth phase-dependent sigma factor. Further studies indicated that there are many genes that are expressed in an RpoS-independent but stationary phase-specific manner. However, proteins represent the functional molecules of the cell. Additionally, protein expression does not always correlate with the corresponding gene expression patterns. Therefore, to obtain an in depth understanding of the proteins that play a role in long-term growth in E. coli, TMT- (Tandem Mass Tags) based quantitative proteomic analysis was performed to identify proteins that are preferentially expressed during prolonged starvation. We identified proteins that were both positively and negatively regulated by RpoS during stationary phase, such as GadA and TnaA, respectively. RpoS levels peaked during early stationary phase and declined thereafter. However, proteins that were RpoS-dependent continued to increase during prolonged stationary phase. Additionally, we identified proteins that were expressed in an RpoS-independent manner during stationary phase. This suggests that protein expression during early stationary phase is distinct from prolonged stationary phase. Furthermore, RpoS-independent proteins may also play an important role during long-term growth. / Thesis / Master of Science (MSc) / Escherichia coli adapts to shifts in nutrient availability using the alternative sigma factor RpoS which controls morphological and physiological changes. Although gene expression during growth has been extensively studied, comparable information regarding changes in protein abundance during prolonged incubation is not available. We employed a quantitative proteomics approach to identify proteins that are preferentially expressed during stationary phase in E. coli. We identified classes of proteins that are upregulated and downregulated by RpoS in addition to proteins regulated independently of RpoS. Global analysis of protein expression during growth can aid in understanding the adaptation of E. coli under starvation conditions.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25302 |
| Date | January 2019 |
| Creators | McFarlane, Nicole |
| Contributors | Schellhorn, Herb, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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