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Abstract
Escherichia coli cells originally exposed to a single stress develop resistance to further environmental stresses. This is referred to as the cross protection phenomenon and is regulated by RpoS, a master regulator of the general stress response. Using a cell viability + assay, the focus of this study was to determine whether wildtype ( rpo S ) and mutant – ( rpo S ) E. coli cells exposed to a high temperature (42.5°C) will exhibit resistance to a subsequent osmotic shock at 2.5 M NaCl. The results indicate that regardless of the type of treatment (e.g. heat shock and/or osmotic shock) applied to the rpo S mutant strain, significant decreases in cell viability were observed. In addition, the constant level of cell + viability observed by rpo S E. coli cells that underwent the sequential shocks in comparison, further indicates cross protection was conferred for some time. These findings support our hypothesis in that the cross protection phenomenon is regulated through an RpoS dependant mechanism.