The Regulatory Functions of the Multiple Alternative Sigma Factors RpoE, RpoHI, and RpoHII Depend on the Growth Phase in .

Bacterial growth, under laboratory conditions or in a natural environment, goes through different growth phases. Some gene expressions are regulated with respect to the growth phase, which allows bacteria to adapt to changing conditions. Among them, many gene transcriptions are controlled by RpoHI or RpoHII in . In a previous study, it was proven that the alternative sigma factors, RpoE, RpoHI, and RpoHII, are the major regulators of oxidative stress. Moreover, the growth of bacteria reached a stationary phase, and following the outgrowth, and mRNAs increased with respect to the growth phase. In this study, we demonstrated the regulatory function of alternative sigma factors in the gene. The gene is expressed with respect to the growth phase and belongs to the RpoHI/RpoHII regulons. Reporter assays showed that the antisigma factor ChrR turns on or over the RpoE activity to regulate expression across the growth phase. In the exponential phase, RpoHII and sRNA Pos19 regulate the expression of to an appropriate level under RpoE control. In the stationary phase, RpoHI and Pos19 stabilize the transcription of at a high level. During outgrowth, RpoHI negatively regulates the transcription of . Taken together, our data indicate that these regulators are recruited by cells to adapt to or survive under different conditions throughout the growth phase. However, they still did not display all of the regulators involved in growth phase-dependent regulation. More research is still needed to learn more about the interaction between the regulators and the process of adapting to changed growth conditions and environments.