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Abstract
The effect of sucrose-induced osmotic stress on Escherichia coli cells is mediated by the regulation of cAMP synthesis. Previous studies concluded that hyperosmotic stress induced by ionic solutes will lead to an increase in the cAMP levels in the cell as a response to changes in osmolarity; however, such conclusions could not be made for osmotic stress induced by non-ionic solutes such as sucrose. To determine whether the global regulator cAMP receptor protein (CRP) plays a role in adaptation under hyperosmotic stress induced by sucrose, E. coli cells were grown under varying sucrose concentrations and the growth rate over a three hour period was correlated with the β -galactosidase activity of these cultures. In the absence of sucrose, crp mutants and wild-type strain have similar growth rates. However, crp mutants show increased growth rate when subjected to growth in increased amount of sucrose, while the growth rate for the wild-type is not affected by the increasing sucrose concentration. β -galactosidase assays were performed on the wild-type, crp mutant and crp/lacI double mutant as an indirect assessment of intracellular cAMP levels, but the results were inconclusive due to sucrose-induced turbidity which interfered with absorbance measurements.