In nature, most bacteria survive in non-proliferating state due to the limitation of their access to nutrients. In such state, it has long been recognized that bacteria will progressively lose their viability. The factors determining the death rate of bacteria under starvation condition have been of great interest to scientists. Many of these factors have been very well studied on the molecular level, including the oxidative stress and the anaerobic respiration. In this research, we propose that the ongoing DNA replication in stationary phase is another factor that leads to bacteria death. We used two different methods in this study to compare the viability of cells with ongoing DNA replication and that of cells without such process. We took advantage of a temperature sensitive strain which is not able to initiate DNA replication at 43 °C but can finish ongoing replication at this temperature. Also we used the antibiotic rifampicin to achieve the same purpose. Our result shows that cells without open DNA forks do have extended lifespan under starvation condition. Moreover, we also compared the viability of rifampicin treated wild type cells with RpoS deleted cells. RpoS, a master regulator of stress response, is proved to be necessary in our research for cells to maintain the viability. We expect that the findings provide a new insight into underlying mechanisms of senescence and longevity for bacteria and other organisms.
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About this Honors Thesis
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|Factors Determining the Death Rate of Starved E.coli Cells ()||2018-08-28||