The Expression of Escherichia coli DNA-Binding Protein StpA upon Normal Conditions and Stress Exposure

Abstract

In this work we constructed the translational stpA::lacZ reporter fusion. The expression of the stpA gene was studied on the translational level in Escherichia coli cells grown in rich and defined media upon the standard conditions, as well as upon both the osmotic shock and the nitrogen starvation. The expression of stpA was higher and more stable in defined medium, as compared to the rich one. This difference was more remarkable at the stationary phase. The expression of stpA decreased dramatically upon the osmotic shock and the nitrogen starvation. Furthermore, here we have investigated the polyamine effects on the stpA expression on the transcriptional, translational and posttranslational levels. The stpA expression was mostly upregulated by putrescine. The stimulation of the gene expression on the transcriptional level occurred primarily at the exponential phase, whereas the translational stpA stimulation was dominated at the exponential phase and, to a greater extent, during the cell transition to the stationary phase. The stpA expression on the posttranslational level was primarily affected by putrescine at the exponential and stationary phase. The effects of cadaverine and spermidine were less noticeable.