To compare the transcriptome of ompR null strains with wild-type strain of S. Typhimurium during osmotic stress

In bacteria, one paradigm for signal transduction is the two-component regulatory system, consisting of a sensor kinase (usually a membrane protein) and a response regulator (usually a membrane protein) and a response regulator (usually a DNA binding protein). The EnvZ/OmpR two-component system in S. Typhimurium responds to osmotic stress and regulates expression of outer membrane proteins. Furthermore, bacteria were believed to regulate pH by acidifying after external acid stress, then immediately recovering. Using a pH-sensor in single living cells, we show that S. Typhimurium maintain an acidic cytoplasm under sucrose-driven osmotic stress which requires OmpR. Thus, we set out to identify the OmpR targets of S. Typhimurium under osmotic stress. To identify OmpR targets under osmotic stress conditions, we performed a microarray and compared the transcriptome of ompR null strains with wild-type strains of S. Typhimurium at high osmolality. S. Typhimurium strain was grown in MgM media at 7.2 and 7.2 with 15% (w/v) sucrose to O.D ~0.6. The total RNA was isolated using an RNeasy mini kit (Qiagen) and proceeded for Microarray